

















































































































































































































































































































♦ 
































































. 



. 









I 










* 

WORKS OF 

PROF. A. PRESCOTT FOLWELL 

PUBLISHED BY 

JOHN WILEY & SONS. 


Sewerage. 

The Designing, Construction, and Maintenance 
of Sewerage Systems. 8vo, cloth, $3.00. 

Water-supply Engineering. 

The Designing, Construction, and Maintenance 
of Water-supply Systems, both City and Irriga¬ 
tion. 8vo, cloth, $4 .00. 


v 







SEWERAGE. 


THE DESIGNING, CONSTRUCTION, AND 

MAINTENANCE 

OF 

SEWERAGE SYSTEMS. 


BY 

A: PRESCOTT FOLWELL, 

Member American Society of Civil Engineers; 

Member American Society of Municipal Improvements ; 
Associate Professor of Municipal Engineering, Lafayette College. 


FIFTH EDITION , REVISED AND ENLARGED . 

SECOND THOUSAND. 


NEW YORK: 

JOHN WILEY & SONS. 

London: CHAPMAN & HALL, Limited. 

1904. 


Copyright, 1898, 1900, 1901, 

BY 

A. PRESCOTT FOLWELL. 


't] 


C tv ( ^ « t < * ' 

C % 4L < ‘ « t. *■ V 

f ( C1 \l 4 < 

« CCVcC <*<■ * < 

r tie tc «• 4 < t t 444 


(Ml « i* * •* 
4 c 1 * 

< \ 4 t % * 

t « # e 

( C ( t J * 



fit 

c 

i c 

t 

c < <. 




c t 
f 

t* l 


% 


ROBERT DRUMMOND, PRINTER, NEW YORK. 







PREFACE. 


For a number of years the author has been looking for the 
appearance of a work on Sewerage which should embody the 
most recent data and ideas relating to the subject and treat 
of both the Combined and Separate Systems in a comprehen¬ 
sive manner, recognizing the fact that such a work is needed 
by city engineers and engineering schools. None such has 
appeared, and he has consequently undertaken the task of 
supplying the deficiency. 

No attempt has been made to treat at length the subject 
of Sewage Disposal, fo,r the reasons stated in Chapter II. 
Parts II and III on the Construction and Maintenance of 
Sewers will, he believes, be appreciated by those who are 
calk upon to superintend such work without previous experi¬ 
ence, and even, he hopes, give valuable hints to many who 
are not novices; although he recognizes that the ground is by 
no means completely covered. For much of the matter 
therein contained he is indebted to the engineering peri¬ 
odicals, particularly the News and Record , but the greater part 
of it has never, to his knowledge, appeared in print. 

While primarily intended for practising engineers, the 
work has also been arranged with the idea that it may be 
useful as a text-book in engineering schools; Part I having 
already been so used by the author, and Part II having been 
largely given in the form of lectures to his classes. 

# • • 
in 



PREFACE TO THE THIRD EDITION. 


In response to many requests from instructors and city 
engineers for the addition to “ Sewerage ” of a more extended 
discussion of Sewage Disposal, this subject has been enlarged 
to fill four chapters of considerable length, in place of the 
twelve pages of the first edition. 


PREFACE TO THE FOURTH EDITION. 


The author has taken advantage of the necessity for a 
fourth edition to still further increase the space devoted to 
iSewage Disposal, and to so revise the discussion of this 
subject as to bring it into accord with the latest conclusions 
of the recognized authorities. 





CONTENTS. 


PART I. DESIGNING. 

Chapter I. System to be Employed. 

ART. PAGK 

1. Requirements of a System. i 

2. Dry Sewage Methods. 2 

3. Dry Sewage Systems. 4 

4. Pneumatic Systems. 7 

5. Water-carriage Systems. 7 

6. Combined and Separate Systems. 9 

7. Summary. 12 

Chapter II. Disposal by Dilution. 

8. “ Disposal ” and “ Sewage ” Defined ... 14 

9. Aims of Disposal. 15 

10. Principles Involved... 18 

11. Pollution of Streams and Tidal Waters. 21 

12. Effects of Dilution. 23 

Chapter III. Amount of Sewage. 

13. Sewerage Conduits. 30 

14. Amount of House-sewage. 31 

15. Data of House-sewage Flow. 37 

16. Amount of Storm-water. 44 

17. Rates of Rainfall. 44 

18. Run-off Data. 47 

19. Formulas for Storm-water Run-off. 52 

20. Expediency of Providing for Excessive Storms. 56 


v 
























VI 


CONTENTS. 


Chapter IV. Flow in Sewers. 

ART. PAGE 

21. Fundamental Theories. 60 

22. Limits of Velocity. 73 

23. Size of the Sewer. 78 

24. Shape of the Sewer. 81 

Chapter V. Flushing and Ventilation. 

25. Necessity for Flushing. 85 

26. Methods of Flushing. 88 

27. Appliances for Flushing. 93 

28. Necessity for Ventilation. 95 

29. Methods of Ventilation. 97 

Chapter VI. Collecting the Data. 

30. Data Required. 103 

31. Surveying and Plotting. 106 

Chapter VII. The Design. 

32. General Principles. . m 

33. Subdivision into Districts. 116 

34. Locating the Sewer Lines. 117 

35. Volume of House-sewage.. . 120 

36. Volume of Storm-sewage. 122 

37. Grade, Size, and Depth of Sewers. 131 

38. Inverted Siphons. 138 

39. Sub-drains. 139 

40. House and Inlet Connections. 141 

41. Manholes, Inlets, Flush-tanks, etc. 144 

42. Pumping of Sewage... 148 

43. Intercepting-sewers and Overflows. 153 

44. Use of Old Sewers. 153 

Chapter VIII. Detail Plans. 

45. The Sewer-barrel. 137 

46. Pipe Sewers. 166 

47. Manholes, Lamp-holes, Flush-tanks, etc. 171 

48. Interceptors and Overflows. 183 

49. Inverted Siphons, Sub-drains, Foundations. 185 
































CONTENTS. Vll 

Chapter IX. Specifications, Contract, Estimate 

of Cost. 

ART. PAGE 

50. Definition and Classification of Specifications. 190 

51. Specifications for Materials. 192 

52. “ “ Excavation. 198 

53. “ “ Construction. 202 

54. “ “ Back-filling and Cleaning Up. 212 

55. General Provisions, Payments, etc. 216 

56. Contract. 223 

57. Estimate of Cost. 226 

58. Methods of Assessment.... 231 

PART II. CONSTRUCTION. 

Chapter X. Preparing for Construction. 

59. Contract Work or Day Labor. 237 

60. Obtaining Bids. 239 

61. Engineering Work Preliminary to Construction. 241 

62. Other Preliminaries. 242 

Chapter XI. Laying Out the Work. 

63. Lining Out Trenches. 244 

64. Giving Grade. 245 

Chapter XII. Oversight and Measurement of Work. 

65. Inspection of Work. 252 

66. Duties of the Engineer. 254 

67. Measurements. 256 

68. Final Inspection. .... 260 

Chapter XIII. Practical Sewer Construction. 

69. Organizing the Force. 265 

70. Trenching by Hand. 270 

71. Excavating Machinery. 275 

72. Sheathing. 2 79 

73. Laying Sewer Pipe. 2 9 l 

74. Building Masonry Sewers. 297 

75. Building Manholes and Other Appurtenances. 306 




























Vlll 


CONTENTS. 


ART. PAGB 

76. Foundations. 3°9 

77. Pumping and Draining.310 

78. Handling Wet and Quicksand Trenches.315 

79. River Crossings and Outlets...328 

80. Crossing Railroads and Canals. 335 


PART III. MAINTENANCE. 

Chapter XIV. House Connections and Drainage. 


81. Necessity for Intelligent Maintenance.340 

82. Requirements of Sanitary House-drainage.341 


Chapter XV. Sewer Maintenance. 


83. Requirements of Proper Maintenance.347 

84. Flushing.349 

85. Cleaning. 354 


Chapter XVI. The Sewage Treatment Problem. 


86. Composition of Sewage... 361 

87. Sewage Analyses. 368 

88. Aims of Treatment. 374 

Chapter XVII. Prevention of Nuisance. 

89. Clarification. . 377 

90. Precipitation...;. 378 

91. Precipitating Plants. 388 

92. Cost of Precipitation. 396 


Chapter XVIII. Destruction. 


93. Mineralization. 397 

94. Broad Irrigation. . 407 

95. Crops. 410 

96. Filtration. 412 

97. Cost of Irrigation and Filtration. 417 

98. Contact Filters and Septic Tanks. 419 

99. Other Purification Methods.428 

100. Summary. 429 

Appendix No. i . 431 































CONTENTS . 


IX 


TABLES. 

1. Population and Per Capita Water Consumption in Different 

Cities. . 32 

2. Population, Number per Family and per Dwelling, Different 

Cities. 35 

3. Gaugings of Sewage Flow, Providence, R. 1 . 38 

4. “ “ “ “ Toronto, Canada. 39 

5. “ “ “ “ Schenectady, N. Y. 39 

6. “ “ “ “ Atlantic City, N. J. 39 

7. “ “ “ “ Weston, W. Va., Insane Hospital.. . 40 

8. “ “ “ and Water Consumption, Des Moines, la. 43 

9. Maximum Rates of Rainfall in Various Sections. 46 

10. Relative Cost and Capacity of Sewers, Washington, D. C. 58 

11. Velocity and Discharge in Circular Sewers, 4 to 36 in. Diameter 64 

12. “ “ “ “ “ “ 33 in. to 10 ft. Diameter 66 

13. p , a, R, Velocity and Discharge for Different Depths of Sew¬ 

age, Circular Sewers. 69 

14. /, a, R, Velocity and Discharge for Different Depths of Sewage 

Egg-shaped Sewers. 70 

15. Materials Moved by Different Velocities of Water. 74 

16. Calculation of Sewer Sizes for Minimum Grades... 134 

17. Prices and Weights, Vitrified Clay Sewer-pipe. 227 

18. Prices of Drain-tile. 228 

19. “ “ Light-weight Iron Pipe. 228 

20. Amount of Cement for Laying Different Sizes of Sewer-pipe 228 

21. Cost of Excavating, Back-filling, and Sheathing Trenches. 229 

22. Cost of Laying Sewer-pipe . 229 

23. Cost of Circular Brick Sewers. 230 

24. Cost of Manholes . 230 

25. Amount of Excremental Organic Matter in Sewage . 362 

26. Analyses of Sewage of Several Cities. 371 

27. Results of Treating Sewage with Lime. 379 

28. Results of Chemical Precipitation. 383 

29. Analyses of Sewage Sludge. 394 

ILLUSTRATIONS. 

PLATE 

I. Des Moines Sewer Gaugings and Water Consumption. 41 

II. New Orleans Run-off Curve Diagrams. 49 

III. Plan of a House-sewerage System. 123 

IV. Rainfall Diagrams and Acreage Curve. 125 

V. Plan of a Storm Sewer System ... ... .•. 128 

VI. Sections of Masonry Sewers. 160 

VII. “ “ “ “ . 162 





































X 


CONTENTS . 


PLATE PAGE 

VIII. Sections of Masonry and Pipe Sewers... 164 

IX. Manholes and Lamp-holes. 173 

X. Manholes, Flush-tanks, and Inlets... 175 

XI. Interceptors, Siphons, Sub-drains, etc. 184 

XII. Trestle Excavating-machine at Work. 277 

XIII. Normal Chlorine in Massachusetts and Connecticut. 365 

FIGURE 

1. Modified Birmingham Pail . 5 

2. Egg-shaped Sewer. 82 

3. Sounding-rod. 109 

4. Alignment of Sewer Junctions. 119 

5. Method of Setting Grade-plank. 246 

6. “ “ “ “ “ . 247 

7. “ “ Holding Grade-cord. 248 

8. Grade-rod. 248 

9. Inspector’s Templet, Egg-shaped Sewer. 262 

10. Invert-former.. 263 

11. Excavation-platform. 271 

12. Cross-staging in Trench. 272 

13. Skeleton Sheathing . 281 

14. Sheathing under Braces. 283 

15. Driving-cap and Maul. 285 

16. Horizontal Sheathing. 285 

17. Sliding Rod for Measuring Braces. 287 

18. Sheathing Puller.. 289 

19. Pipe-laying Hook. 292 

20. Appliance for “Entering” Heavy Pipe. 292 

21. Pipe-cleaning Disk. 295 

22. Templet for Brick Sewers... 298 

23. Hod for Lowering Brick. 300 

24. Mason’s Platform for Brick Sewers. 301 

25. Centre for Brick Sewers. . 302 

26. Form for Concrete Arch. 305 

27. Sewer-pipe Laid in Concrete. 319 

28. Sheathing a Badlv Caved Trench. 321 

29. Appliance for Cleaning Sub-drains. 326 

30. Sewer Crossing Creek above Water. 329 

31. Coffer-dam Puddle Walls. 333 

32. Sheathing on Steep Slopes. 337 

33. Flange for Pipe in Embankment. 338 

34. Appliance for Cleaning Siphon-sump.. 355 

35. Disk for Cleaning Sewers. 357 

36. Method of Using Cleaning-disk. 358 

37. Chicago Vertical-flow Tank.390 

38. interior of Champaign Septic Tank. 424 














































SEWERAGE. 


CHAPTER I. 

THE SYSTEM. 

Art. 1 . Requirements of a System. 

A SYSTEM for the removal of sewage is demanded by a 
populous community on two grounds: the higher one of the 
public health, and the more popular one of convenience; and 
in designing a system each of these purposes must be kept 
constantly in mind, the first being ever given predominance 
over the second if they conflict in any way. The proper 
meeting of these demands determines the principles of 
designing. 

There are two imperative essentials to sanitary sewerage: 

I. That the sewage, and all the sewage, be removed with¬ 
out any delay to a point where it may be properly disposed 

of. 

II. That it be so disposed of as to lose permanently its 
power for evil. 

Convenience requires that the sewage be collected and 
disposed of with the least trouble to the householder and in 
the least obtrusive and offensive way. 

In taking up the study of sewerage for any particular 
place or community the first question arising is the general 



2 


SEWERAGE . 


system to be adopted. In many cases financial limitations 
will be forced upon the engineer as an unfortunate but im¬ 
perative argument in the choice not only of the details of the 
system but even of the system itself. He must perforce 
recognize these limitations in addition to the requirements of 
sanitation and convenience, but should not carelessly assume 
that since there is but little money to spend upon the work 
the care given to the design will need to be only proportion¬ 
ately great. He should realize that the highest talent is 
needed to obtain the best results with limited resources. 

The solution of the difficulty when a complete water- 
carriage system is rendered out of the question by reason of 
its cost may lie in the construction of only the most neces¬ 
sary portion of the system or in the adoption of one of the 
dry-sewage systems. 

Art. 2. Dry Sewage Methods. 

The methods in common use for removing excrement and 
liquid wastes may be conveniently divided into three general 
classes: (i) Dry Sewage, (2) Pneumatic, and (3) Water-car¬ 
riage systems. 

The most primitive method of application of excrements 
to the soil—if it can be called a method—would be embraced 
under the first head. The old-fashioned privy was a step 
forward, and in a large part of this country is as yet the only 
one which has been taken, privacy being the main argument 
for its adoption. But, while contributing somewhat to this 
and to comfort, it cannot be considered as a sanitary appli¬ 
ance. “ Constructed for the avowed purpose of retaining the 
solid matters as long as possible upon the premises, they 
become centres of pollution and infection. The liquid por¬ 
tions, escaping, pollute the soil and neighboring wells; the 
noxious exhalations arising from their putrefying contents 


THE SYSTEM. 


3 


contaminate the air.” (Samuel M. Gray’s Report on Pro¬ 
posed Sewerage System for Providence, R. I.) 

Regular movement of the bowels is essential to health and 
to bodily and mental vigor. Yet a rainy day, a deep snow, 
or publicity of location has kept many a person from the daily 
attention to nature’s demands when this requires a visit to 
the outdoor privy. 

This last objection is met by the indoor closet connected 
with a cesspool; but there is probably no subject upon which 
sanitarians are more thoroughly agreed than upon the inher¬ 
ent vileness and danger of the cesspool as ordinarily con¬ 
structed. Fresh sewage if not taken into the stomach is 
neither injurious to health nor very offensive to the smell; 
but from putrescent excreta and kitchen slops come those 
noisome gases which, if not themselves bearers of malefic 
germs, at least lower the vitality and render the body more 
vulnerable to disease. Retained for weeks and months in a 
liquid or semi-liquid state in a cesspool, sewage is then under 
the conditions best adapted to putrefaction in its foulest form. 
And in very few, if any, cases is the plumbing of the house 
adapted to exclude from the air of the dwelling the gases 
emitted; indeed it is doubtful if this can be accomplished 
with certainty when, as is too often the case, the cesspool is 
tightly covered or sealed with snow or ice. Moreover, prac¬ 
tically no cesspools are water-tight, though many are thought 
to be so. A cesspool feet in diameter and io feet deep 
to which a family of five contribute a daily average of 25 
gallons of sewage (a low estimate) would, if tight, require to 
be cleaned twice each year. Very few, it is believed, are 
cleaned this often; many are never cleaned, but the contained 
liquid leaches out into and through the adjacent soil, which 
soon loses its power to purify it. 

This vilest of liquids is dangerous in two ways: it may 
reach and taint wells for hundreds of feet around, and it may 


4 


SEWERAGE. 


pollute the air existing in the soil under cellars, which air will 
exhale and permeate the houses above. In excavating for 
sewers in gravelly soil in a city street the author has found 
the gravel colored black by the liquid from a cesspool located 
75 feet distant in the rear of the house opposite; which 
liquid must consequently have passed under or around the 
cellar of this house. 

It seems advisable to speak thus at length on this subject 
for the reason that many intelligent persons look with favor 
on the cesspool as a sanitary contrivance, whereas in most 
cases it is one of the greatest abominations permitted in any 
civilized community. (See note, page 13.) 

Art. 3 . Dry Sewage Systems. 

The methods already referred to can hardly be called 
systems, but are rather makeshifts. The simplest systems 
which can be at all commended are the Pail system and the 
Earth-closet. These are used but little in this country, but 
would be for many small villages a vast improvement over 
the privy or cesspool. 

The Pail system consists essentially of the placing under 
the privy-seats of pails, which are to be removed, emptied in 
some spot where a nuisance will not thereby be created, 
cleaned, and returned. Duplicate pails must be provided to 
be used in place of these during their absence. 

This method is in use at Marseilles, Havre, and other 
French cities; at Rochdale, Birmingham, Manchester, and 
other places in England; but only in certain districts of these 
cities, which are introducing water carriage and are yearly 
increasing the territory thus sewered. It has been used by 
a few communities in this country also, among them Vine- 
land, N. J., Memphis, Tenn., Atlanta, Ga., and Warren, O., 
but is being replaced in these with water-carriage systems. 


THE SYSTEM. 


5 


A modification of and improvement upon the Pail system 
is the Earth-closet system, in which pulverized dry earth, 
charcoal, or ashes are used as a deodorizer and are applied to 
the excreta while fresh, the mixture being subsequently 
removed, preferably as in the Pail system. Brick-clay and 
loam rank high as deodorizers when applied in a perfectly 
dry and powdered state. Ashes are not so effective. In 
Bremen powdered turf is used. There is not evident a suffi¬ 
cient superiority in charcoal to compensate for its cost and 
other disadvantages. 

The deodorizing-powder should be applied each time the 
closet is used. An excellent arrangement is that of a large 
box or barrel resting upon an extension of the seat and with 
an aperture and slide so contrived that any desired amount 
of the powder may be deposited upon the excrement by a 



Fig. Xi —Modified Birmingham Pail. 

slight motion of a convenient handle. The simplest method 
of applying the deodorizer is by a small scoop or shovel, the 
earth being kept in a box placed in a convenient position in 
the closet. 

For either the Pail or Earth-closet system the receptacle 
should be round, as this form is more easily cleaned than a 
square one; and preferably of metal, as a wooden pail soon 





































6 


SEWERAGE. 


becomes saturated with foul liquors. A good form is that of 
the modified Birmingham pail. The pails should be thor¬ 
oughly cleaned after each emptying. If the earth closet is 
used a thin layer of earth should be spread over the bottom 
of the pail when it is replaced under the seat. 

The mixture of earth and excreta may be dried and used 
again; but there is a possible danger in this, since bacteria 
are not often destroyed by moderate heat; it will probably 
be found more convenient also to deposit it immediately upon 
the garden or field as a fertilizer. If the Pail or Dry-earth 
system is adopted for a village or city an arrangement may 
be made by contract for removing the buckets or tubs at 
intervals of not more than a week, the material to be disposed 
of by the contractor. Such disposition of it should be made 
—either by placing it directly upon the fields; or by drying 
and pulverizing it, in which form ( poudrette ) it is more con¬ 
venient for use as a fertilizer; or by burning it (see Chapter 
ii) —as will avoid the creating of a nuisance (see Art. io). 

There are several methods, some' patented, for disposing 
of dry sewage and garbage on the premises by means of heat, 
by either drying or cremating. The heat for these is 
obtained either from a furnace constantly burning, in which 
case its use in summer is exceedingly inconvenient and is 
usually dispensed with; or by occasional fires lighted at long 
intervals, during which the waste matter undergoes dangerous 
putrefaction. On account of these and other equally serious 
objections these methods are not to be commended, particu¬ 
larly since the cost, were every house to adopt them, would 
in most locations suffice to construct an excellent water- 
carriage system. 

These dry-sewage systems, though improvements on the 
privy and cesspool, are imperfect from a sanitary point of 
view in that they require the excreta to be stored about the 
premises for a certain period, and because they fail to pro- 


THE SYSTEM. 


7 


vide for the removal of slops and sink-water and dispose of 
urine to a limited extent only. Neither do they provide 
for the drainage of the soil nor for the removal of surface- 
water. Convenience also is not fully served by their use. 

Art. 4. Pneumatic Systems. 

In the Pneumatic systems the faeces only are removed, 
the house drainage, surface- and subsoil-water requiring a 
separate system of sewers or utilizing the gutters. The most 
widely known of these are the Liernur and the Berber—the 
first used principally in Holland, the second in Paris. These 
two are practicable under certain conditions only and will not 
be described at length. Their object is to remove the sew¬ 
age at frequent intervals through pipes, by means of com¬ 
pressed air or a vacuum, to a central station, there to be 
disposed of in some way, usually by being manufactured into 
a fertilizer. The great cost of these is prohibitive to their 
introduction into small cities and towns, and on account of 
their limited applicability, as well as for practical and sanitary 
reasons, their adoption in future designs is improbable. 

The Shone system, which is used to some extent in 
England and her colonies and in this country, although 
classed among the Pneumatic systems, is really not in itself a 
system, but an application to the water-carriage system of a 
method of pumping sewage by the direct action of com¬ 
pressed air. It will therefore be considered under the head 
of the Water-carriage System. 

Art. 5. Water-carriage System. 

The Water-carriage system has now been so almost uni¬ 
versally adopted where any improvement upon the primitive 
privy has been attempted that the term “ Sewerage System ’* 


8 


SE WEE A GE. 


I 


is ordinarily used without further qualification to refer to it. 
When properly constructed and managed it is certainly 
deserving of its popularity, being the best and cheapest 
method yet contrived for the removal of sewage. 

As its name implies, its distinctive characteristic is the 
removal through conduits, by gravitation, of sewage which 
has been greatly diluted with water. It meets the first 
principal requirement of a sanitary system (Art. l)—it 
removes all house-wastes and removes them immediately. It 
;aiso serves the secondary but by no means unimportant pur¬ 
pose of removing the surface-water and draining the ground. 
Its convenience also is excelled by no other system. More¬ 
over, where the territory is quite thickly populated—as in 
the average town—it is in the end cheaper than any other 
system. The two most weighty arguments against it are the 
large amount of water needed for its efficient working, and 
the pollution of streams and waste of the valuable manurial 
properties in the sewage when this is emptied into river or 
sea, as is frequently done. Victor Hugo in his “ Les 
Miserables ” devotes a long chapter to the “Crime of the 
Century” involved in this waste. But whether this matter 
is ultimately wasted or its use by man only deferred it is not 
necessary to discuss.* The all-convincing argument with any 
but the sentimentalist is that, while there may be manurial 
value in sewage, no commercially profitable method of utili¬ 
zing it has yet been found. The best disposition to be made 
of it is therefore that which is least harmful, unpleasant, and 
expensive, and in most cases water carriage enables us to 
provide such disposition. 

The argument that its proper working involves the use of 
large quantities of water is undoubtedly true. But where 
water-works already exist this objection has little force—less 
in this country than abroad, where 20 to 40 gallons per capita 
is considered a liberal allowance for water-consumption; 


* See page 24, last paragraph. 






THE SYSTEM. 


9 


while in this country our small cities must provide two or 
three and the large ones five or six times this amount, which, 
with in many cases a small percentage additional for flushing, 
is usually sufficient and no difficulty is found in providing it. 
Some expense, however, is frequently incurred for flushing- 
water and to this extent is there force to the objection. 

Places which are without a general water-supply or the 
general use of individual power-supplies are barred from the 
adoption of the Water-carriage system. For such the best 
plan is to adopt the Earth-closet system until such time as 
water has been introduced into most of the dwellings, when 
a Water-carriage system may be initiated, the Earth-closet 
pails being continually relegated, as the conduit system is 
extended, to the outskirts of the town, where the growth will 
probably keep a year or two ahead of the water-supply and 
sewer-construction. 

Other objections are sometimes raised to the Water- 
carriage system which are either equally applicable to all 
systems or which are the result of prejudice. The possibility 
of the introduction into dwellings, through the house-connec¬ 
tions, of sewer-air (which is not a “ gas ”) is one of these, 
and is certainly a real one. But the resulting danger is not 
so great as that connected with similar evils of other systems, 
and it is preventable by careful designing and construction of 
the sewers and house-plumbing. 

Art. 6. Combined and Separate Systems. 

It is generally conceded by sanitarians that where the 
conditions render it possible the Water-carriage system should 
be adopted. This system, however, has .been subdivided 
into the Combined and the Separate systems. The terms 
“ Combined” and “ Separate” refer to the two classes of 
waters which it is desirable to remove—rain-water and house- 


10 


SE WEE A GE. 


sewage. In the former system these are carried in a common 
conduit; in the latter the house-sewage is removed through 
small sewers, the storm-waters through other large ones or in 
the gutters, or partly in one and partly in the other. 

The comparative merits of these is a theme much dis¬ 
cussed and upon which unanimity of opinion has not yet been 
entirely reached. It will most probably be reached by 
mutual concession, for there are undoubtedly substantial 
arguments in favor of each. In some cases the one, in some 
the other, is most applicable. In many, if not a majority of, 
instances a judicious combination of the two will work to 
better advantage than either alone. ♦ 


There is neither space nor necessity to quote in this work 
all the arguments advanced for and against each of the 
systems, or even to attempt to specify them all in detail, 
since the systems will be treated as cooperative rather than 
as rivals; for such is the relative position now assigned them 
by the best authorities. Their respective advantages under 
varying conditions will be treated of in Chapters III and VII. 
It may be well, however, to give in this connection a short 
statement of the points at issue between the two systems. 

Either system must, if providing for storm-water, include 
sewers of large size—2, 3, even 15 or 20 feet in diameter. 
Yet during nine tenths of the time the amount of sewage 
flowing is no more than could be carried by pipes of from 4 
inches to 2 feet in diameter. 


(1) In the Separate system 
.pipes of that size are used for 
the daily sewage, and thus 
greater velocity secured with 
a given amount of sewage and 
a given grade; consequently 
cleaner sewers. 


(2) But even these will at 
times stop up, and then there 
may be some difficulty in re¬ 
moving obstructions from the 
pipes. Obstructions in the 
large sewers on the other hand 
can be readily reached and 
removed. 



THE SYSTEM. 


II 


(2) But in the Separate 
system the storm-sewers may 
frequently be placed only 3 
to 5 feet below the surface, 
while in the Combined they 
must be low enough to receive 
the house-sewage — usually 
from 8 to 12 feet belowthe sur¬ 
face. The resulting increase 
in cost would often more 
than cover that of an addi¬ 
tional system of small house- 
sewers. Moreover, towns too 
poor to put in large Combined 
sewers can for one third to 
one fifth of their cost remove 
their daily sewage alone by 
means of small pipes. 

(2) But flushing would im¬ 
prove Combined Sewers also, 
and would probably be em¬ 
ployed if the amount of water 
necessary to keep them clean 
were not, through its vastness, 
prohibitive,unless it can be in¬ 
troduced from a river or other 
large body of water, a plan 
which is sometimes adopted. 

(2) If each is running full; 
but with a given amount of 
sewage the larger sewer must 
have the steeper grade if the 
same velocity is to be ob¬ 
tained. 


(1) In the Separate sys¬ 
tem the storm-sewers must be 
as large as those of the Com¬ 
bined and an additional small 
sewer be provided at a cost 
which increases by its full 
amount the cost of the Sepa¬ 
rate over that of the Combined 
system. 


(1) The Separate system 
usually requires large quanti¬ 
ties of water for its perfect 
operation. 


(1) For small sewers steep¬ 
er grades are necessary than 
for large ones. 





12 


SEWERAGE. 


(2) But this fault (when it 
is a fault) is one of the de¬ 
signer, and not of the system. 


(1) There is a tendency in 
using the Separate system to 
allow storm-water to run for 
long distances upon the street- 
surface. 

(2) But foul air is more 
diluted in large ones. 

(2) But on the other hand 
street-washings are often as 
foul, though not usually as 
dangerous, as house-sewage, 
and should be purified. 


(1) Ventilation is more 
rapid in small sewers. 

(1) A very important ar¬ 
gument in favor of the Sepa¬ 
rate system, and one which 
has the backing of the law in 
many States, is the practical 
necessity for its use where 
treatment of the house-sew¬ 
age is either immediately 
necessary or may in future be¬ 
come so. 

Many other arguments have been advanced on both sides, 
but the most weighty in favor of the Combined system are: 
its economy in first cost over two Separate systems, and the 
ease with which obstructions can be removed and a general 
examination of its contents made; in favor of the Separate 
system: its being self-cleansing, its adaptability, as a house- 
sewage system only, to small and poor towns, and its necessity 
to an economical sanitary treatment of the house-sewage. 


Art. 7. Summary. 

The proper conclusion in reference to the system to be 
adopted would seem to be—the water-carriage, where its 
expense is not prohibitive and the dwellings are abundantly 
supplied with water. In a few exceptional cases a Pneumatic 
system might be preferable. But better than the cesspool or 
privy, if the cost or the water-supply is peremptorily limited,. 






THE SYSTEM. 


13 


would be a dry-sewage system—preferably the dry-earth. 
The last is described to a sufficient length in this chapter, 
as the proper conduct of it requires little else than cleanliness 
and faithful attention. The disposal of sewage thus collected 
will, however, be referred to in Chapter II. 

The water-carriage system is more complicated in design, 
in construction, and in operation; and to the consideration of 
this system the remainder of this work will be devoted. 

Note. —The general adoption of the septic tank (see Art. 98 ), which has 
been called the “ glorified cesspool,” can not properly be-used as an excuse 
for the cesspool. In reality the two differ in every essential. In no satis¬ 
factory septic tank does the sewage remain longer than twenty-four or at 
most forty-eight hours. Even then there are given off large quantities of 
gases which no one would think of piping into his house, as is practically 
done from most cesspools. A comparison of cesspool with septic tank does 
not touch upon the objection to the former that its use scatters a large 
number of centres of soil-pollution throughout a closely populated area. 


CHAPTER II. 


DISPOSAL BY DILUTION. 

Art. 8. “ Disposal” and “Sewage” Defined. 

The word disposal is often used where treatment would 
be more properly employed. As a matter of fact all sewage, 
■dry or water-carried, must be disposed of in some way after 
having been collected by a sewerage system. But if this dis¬ 
posal consists of anything other than throwing away the 
sewage this may be properly called a treatment thereof. 
These words will be thus used in this work —disposal as a 
general term, treatment as a more specific one. 

For a proper consideration of the various methods of dis¬ 
posal it will be necessary to understand the results aimed at 
and the princ'ples involved. And first we must understand 
what is implied by the word sewage. In the dry sewage and 
pneumatic systems it means human excreta and nothing else. 
In the water-carriage system, however, sewage may be found 
to contain almost every description of waste matter: faeces, 
house-“ slops,” manufacturing waste-waters and acids, drain¬ 
age of stables, piggeries, and slaughter-houses, waste paper and 
rags, and frequently “ swill,” and numberless matters which 
should never reach the sewer. This is ordinarily called house- 
sewage. Into combined and storm sewers, besides rain¬ 
water, not only horse-droppings and vegetable refuse but 
sand, clay, gravel, and other heavy matters find admission 
through the street-inlets. These go to make what is called 
storm-sewage. The common impression is that of these the 
human excrements alone are dangerous; and this is to a large 


14 


DISPOSAL BY DILUTION. 


15 


extent true so far as concerns dissemination of the germs of 
disease. But it is known that, aside from this, kitchen-wastes 
are fully as objectionable, since they contain practically the 
same putrescible matter, and in a state less easily rendered 
innocuous by either natural or artificial means. Where storm¬ 
water is admitted to the sewers the large quantities of horse- 
droppings which are washed in during the first few minutes 
of each rainstorm render the water nearly as offensive, if not 
so dangerous, as do human excreta. 

Owing to diversity of manufacturing industries, to differ¬ 
ences in the characters of the water used by different towns, 
and to other local peculiarities the sewage of each town varies 
from that of almost every other. Therefore the question of 
the proper disposal of this compound is seen to be a problem 
of no easy solution. The difficulty of treatment is increased 
by the exceeding dilution of the sewage, since the sewage of 
an average American town will contain but about 1 part in 
1000 of organic matter, I part of mineral matter, and 998 
parts of water. 

Difficulty of disposal is frequently considered to be con¬ 
nected with house-sewage only. But if the separate system 
be used it is generally desirable to connect with the house- 
sewers, cab-stands, market-places, and other parts of streets 
liable to collect considerable filth, small inlets being used, so 
that only a small amount of water from any storm can enter 
them, or else special traps, ordinarily closed, but through 
which the filth can be washed by hose. 

Art. 9. Aims of Disposal. 

The first aim is the getting rid of the sewage; the dispos¬ 
ing of it in such a way and such a place that it will not create 
a nuisance. Communities, being even more selfish than indi- 


16 


SE WEE A GE. 


viduals, seldom regard the well-being of other communities, 
but are satisfied if no nuisance is created within their own 
limits. It is here that the State, by its laws and through its 
Board of Health, should interfere for the protection of each 
community against all others. In England this protection is 
afforded by national laws and a national board. In this 
country many States afford a certain amount of such protec¬ 
tion, varying from that given by the excellent laws of Massa¬ 
chusetts down to the almost total lack of any such protection 
which exists in many of even the older States. It is a duty 
which the engineer owes to humanity to educate the people 
to the importance of this matter; though he will often be 
compelled to yield, in part at least, to the selfish demands of 
those for whom he acts, that they be put to no expense for 
protection of other communities not required by State or 
national laws. 

Where this protection is afforded through adequate laws 
properly enforced the disposal of the sewage must be such 
that it will “ lose permanently its power for evil.” How 
this can best and most economically be done is the question 
to be solved. 

Many attempts have been made at a solution of this ques¬ 
tion of disposal which shall not only meet the sanitary 
requirements, but which shall also be financially remunerative. 
Some reports of success have been heard of, but when investi¬ 
gated the details are found to be disappointing. An English 
company which used a method of Chemical Precipitation was 
reported as paying dividends, but inquiry showed that these 
were but a part of the sum paid to the company by the dis¬ 
trict for disposing of its sewage, and the taxpayers were but 
little benefited in pocket by the method employed. Investi¬ 
gations of other cases have resulted somewhat similarly. The 
author knows of no case where the disposal of sewage is 
accomplished at a profit to the city or town. In the case of 





DISPOSAL BY DILUTION. 


17 


water-carried sewage this is not to be wondered at, since the 
value of the manure contained in one ton of Boston’s sewage, 
for instance, is estimated to be but one cent. 

An exception must be made, however, in the case of the 
Liernur system. It is reported of the manufacture of pon- 
drette from a portion of St. Petersburg’s sewage (collected 
by the Liernur system) that “ it is a groundless assertion 
that the manufacture of poudrette does not cover the costs.” 
It is possible that the force of this statement should be modi¬ 
fied by accenting the word “ manufacture.” But the official 
reports of the city of Amsterdam (where the Liernur system 
is used) state that “ the value of the dust-manure made from 
the sewage covers the whole working expense of the system 
and leaves a considerable margin besides.” (Report of Charles 
Jonas, United States consul-general in 1894.) This is un¬ 
doubtedly accounted for by the fact that faeces only are col¬ 
lected unmixed with water or unmanurial matter. As stated 
before, this system does not fully meet the sanitary require¬ 
ments and is not adapted to this country, accustomed as we 
are to the abundant use of water and to modern conveniences. 

The sewage of several of our Western cities situated in the 
“ desert ” region is disposed of for irrigation at a considerable 
profit. Los Angeles, Cal., received in 1895 a net revenue 
therefrom, above all salaries and repairs, of $1140, and in 
1896 of $943.30, and in 1900 of about $3500. Pasadena, 
Cal., in 1899 raised $2192.89 worth of hay on 157 acres, 
$2984.88 worth of walnuts on 60 acres, and received $701.25 
from other products, or a total of $5942.92 ; the cost of main¬ 
tenance being $2915.02, The total cost of farm (300 acres) 
and implements was about $77,000. Altoona, Pa., received 
in 1898 $100 rental for their sewage farm; and in 1901 $300 
for the privilege of farming 12 acres of farm and 64^ acres of 
filter-beds. In general, few, if any, farms in districts where 


i8 


SEWERAGE. 


irrigation is not necessary, and on which sewage must be 
turned in rainy as well as in dry weather, will bring any con¬ 
siderable rental; and no other system of treatment is known 
which will return any net profit above running expenses. 
This being the case, the endeavor should be to find for each, 
place that method of disposal which, under the existing con¬ 
ditions of location, character of sewage, etc., will best meet 
the requirements both of the State laws and of the laws of 
sanitary science, and which will be least expensive, both first 
cost and maintenance being considered. 


Art. 10. Principles Involved. 

For an exposition of the principles involved we must call 
upon chemistry, biology, bacteriology, medicine, and kindred 
sciences. Their teachings, stated generally, are: 

That matter in a state of putrescence is harmful to human 
life if taken into the system. 

That volatile emanations from such matter when breathed 
into the lungs lower the tone of the constitution and render 
it more susceptible to, if they do not indeed directly occasion, 
disease. 

That many diseases may be contracted by taking into the 

stomach certain germs which are found to be excreted by 

/ 

those already sick of such a disease, and these germs will 
exist for days in sewage having any amount of dilution. 

That ordinarily sewage does not putresce until from 
twenty-four to sixty hours after its discharge, or even longer 
under certain circumstances, such as absence of moisture. 

That the only true destruction of the dangerous character¬ 
istics of sewage is that effected by oxidation and by removal 
of the disease-germs. 

That oxidation does not destroy but merely transforms 


DISPOSAL BY DILUTION. 


19 


the putrescible organic matter into harmless mineral com¬ 
pounds. 

The legal principles involved vary in different localities 
and with different interpreters of the law, frequently depend¬ 
ing upon the ruling as to what creates a nuisance. “ I should 
include under this head any matter, whether solid, liquid, or 
gaseous, which is itself injurious to health or which may 
become so in contact with other substances, whether the 
latter may be in themselves hurtful or not; further, any 
matter which, though not demonstrably poisonous, is offen¬ 
sive to the senses.” (Slater, “Sewage Treatment, Purifica¬ 
tion, and Utilization.”) Such disposition of any matter that 
it may, while in the condition above described, approach 
within effective distance of any dwelling or occupied land 
should be held to be a nuisance. A recent ruling in the 
United States has included in the “ creating of a nuisance ” 
the rendering unfit for drinking purposes water which would 
otherwise be used thus. Under properly prepared State laws, 
interference with the health and rights of others should be 
preventable by injunction, or, in the case of injury to manu¬ 
facturing interests, should subject the city to forfeiture of 
damages. An interesting case under the latter head is that 
decided in 1898 against New York City, and in favor of an 
oysterman whose beds were destroyed by the discharge from 
a near-by sewer outlet, and who was awarded their value in 
damages. (See Engineering Record , vol. xxxvm. page 1.) 
In 1900 the New York Supreme Court decided that an injunc¬ 
tion could be obtained restraining a city from so polluting a 
stream as to injure land or stock, but that damages could not 
be collected from a municipal corporation, although they 
could be from a private one. The Supreme Court of Connec¬ 
ticut stated in a recent ruling: “The discharge of sewage 
and other noxious matters into an inland stream to the injury 
of a riparian proprietor below has been held to be an unlawful 


20 


SEWERAGE. 


invasion of the rights of said proprietor, remediable by injunc¬ 
tion, by the courts of nearly every State, by the federal 
courts, and by the courts of England.” (Morgan et al. vs. 
City of Danbury, Conn.) In 1898 the California Superior 
Court granted an injunction against the city of Santa Rosa 
from emptying into a creek impure effluent from sewage irri¬ 
gation. The Indiana Supreme Court, in 1900, decided that 
a municipality could not be enjoined from discharging sewage 
into any stream. In the same year the Virginia Supreme 
Coujt decided that neither municipal nor private corporations 
can pollute a stream by sewage or otherwise without being 
liable for damages for any injury caused. (See Appendix II.) 

In a few States sewerage systems must be so designed, 
before meeting the approval of the State Boards of Health 
(which is by law made a necessary prerequisite to construction), 
as to permit and provide for a treatment of the house sewage 
at some future time, even if they are allowed temporarily to 
discharge into adjacent streams. It is probable that before 
very many years this will be the regulation in most States. 
But, in any event, where the discharge is into a stream or lake 
the possibility of the necessity arising in the future for treat¬ 
ment of the sewage should be foreseen and provided for in 
the design of the system. It is advisable both to consult the 
State Board of Health and to obtain reliable legal advice 
before deciding finally the question of disposal. 

With these principles in mind a thorough and intelligent 
study of the local conditions should be made to decide how 
the requirements of sanitation and of law may best be met; 
whether any treatment of the sewage will be necessary, and 
if so which is best adapted to the given conditions. 




DISPOSAL BY DILUTION . 


21 


Art. 11. Pollution of Streams and Tidal Waters. 

The simplest solution of the problem, where it is permis¬ 
sible, and the one most frequently employed in this country, 
is to discharge the sewage directly into some flowing stream 
or large body of fresh water, the ocean or one of its estuaries. 
This is called “disposal by dilution.” So far as cheapness 
is concerned this stands easily first among the methods of dis¬ 
posal, since it requires the purchase of no land and needs no 
care to regulate its working, excepting where the discharge 
is into tidal waters, when some expense is frequently gone 
to, both of first cost and of maintenance, to regulate the time 
of discharge. It is usually efficient also in removing the 
sewage beyond the limits of the area contributing to its 
volume. Looked at in a less selfish way, and considering the 
good of the State and country as well as of the locality 
sewered, other and adverse arguments present themselves. 
Although the sewage is removed to a distance from the con¬ 
tributing territory by tides or currents, it may be deposited 
in proximity to other communities, on banks or shores or 
retained by dams, thus creating a nuisance; or may render 
unfit for drinking, household, or manufacturing purposes 
water which would otherwise be so used. 

The effects of sewage pollution of a stream in creating a 
nuisance are well illustrated by the Passaic River. 

“The great extent of the pollution of the lower Passaic 
may be illustrated in several ways. It is apparent to the eye 
in the condition of the river during the summer; in the foul¬ 
ness of the shores where sewage-laden mud, when exposed to 
the sun, gives out foul odors; and it is demonstrated by every 
practical test. The cities of Newark and Jersey City have 
been compelled to seek water-supplies elsewhere at large ex¬ 
pense, and the immediate decrease in zymotic disease in these 
places which has followed the change has shown how neces- 


22 


SEWERAGE . 


sary it is. Fish life, excepting of a few hardy kinds, has dis¬ 
appeared from the river, and fifteen years ago shad, which 
formerly frequented the stream, abandoned it. The manu¬ 
facturers have reported that the acid of the sewage-laden 
water affected boilers so as to make its use inadvisable. The 
use of the river for pleasure purposes, which at one time made 
it a delight to thousands, has become comparatively infrequent, 
and the attractiveness of the river may be said to have disap¬ 
peared.” (Report of the Passaic Valley Sewerage Commission, 
1897.) While this is an extreme case, there are many others 
in this country almost as bad ; and as the country becomes more 
thickly populated other streams will become similarly polluted. 

The mortality due to sewage-polluted water may occur 
through almost any enteric disease, but the greatest is prob¬ 
ably from typhoid fever. An illustration of the mortality from 
this disease due to sewage is found in the city of Lawrence, 
Mass., which uses the Merrimac River as a source of supply, 
which river receives the sewage of Lowell, nine miles above. 
Since August 1893 the supply has been filtered and the result 
is apparent in the following table. 


MORTALITY FROM TYPHOID FEVER IN LAWRENCE, MASS. 


Y ear... 

1885 

1886 

OO 

00 

M 

1888 

M 

00 

00 

VO 

1890 

1891 

1892 

Deaths from typhoid 
per 10,000 inhab- 
itants. 

4.2 

5-75 

11.44 

11.36 

12.66 

13-44 

11.94 

10.52 

Year.... 

1893 

1894 

1895 

1896 

1897 

1898 

M 

00 

vO 

vO 

1900 

Deaths from typhoid 
per 10,000 inhab¬ 
itants . 

7.96 

4-75 

3-07 

1.86 

1.62 

1-39 

3-38 

1.76 


(See also Art. 9 of the author’s work on “ Water-supply 
Engineering. ”) 














































DISPOSAL BY DILUTION. 


23 


Another illustration was the epidemic of typhoid fever 
which, in the winter of 1898—99, visited two or three cities on 
the Passaic River which, for a few days when the supply of pure 
water ran low, pumped water from this river into their mains. 

In this connection reference should be made to the danger 
of spreading certain diseases through the agency of oysters, 
and that of the destruction of fish by disposing of sewage by 
dilution. There seems to be little doubt that typhoid and 
probably other fevers have been so conveyed by oysters, as 
at Wesleyan University, Middletown, Conn., in 1894, and at 
Brightlingsea, England, oysters from the latter place being 
accused on good evidence of having caused twenty-six cases 
of typhoid fever in 1897. These were exposed, however, 
to contact for hours at a time, at low tide, with sewage but 
little diluted. In view of this and of similar cases both in 
this country and abroad it would seem advisable that precau¬ 
tions be taken by the authorities to protect oyster-beds from 
sewage or to prevent the gathering of oysters from sewage- 
contaminated waters. 

It is probable that germs of enteric diseases are conveyed 
on the outside rather than the inside of the body of the 
oyster, and that there is little danger in eating sewage-fed 
fish or cooked shellfish, since the organic matter is digested 
by them and converted into healthy tissue, and such bacteria 
as enter the digestive organs are either destroyed or leave at 
once in the excrement. A moderate amount of fresh organic 
matter attracts most kinds of fish which live upon it or upon 
the minute animal and vegetable life of which it forms the 
food ; but the gases of putrefaction are poisonous to animal life. 

Art. 12. Effects of Dilution. 

Legal and sanitary considerations make it desirable to 
determine whether any amount of dilution of sewage renders 
it innocuous, and whether a river, lake, or body of salt water, 


24 


SEWERAGE. 


whether with or without currents, which has once been pol¬ 
luted will naturally purify itself. Dead organic matter at 
temperatures between 35 0 and 120° is attacked by bacteria 
which decompose it and enable its elements to unite with 
others to form new compounds. If oxygen is present in suf¬ 
ficient quantity, odorless and harmless mineral compounds are 
formed. Such of the elements of the decomposed organic 
matter as are not supplied with oxygen will, in most cases, 
form obnoxious and poisonous hydrogen compounds, among 
these being sulphuretted hydrogen and marsh-gas, which cause 
the floating bubbles seen on the surface of foul water. Most 
waters contain considerable free oxygen, and if the amount of 
this in any given body of water is sufficient to oxidize all 
the sewage reaching it, the organic matter will very shortly 
be decomposed without offence and lose permanently its 
power for evil. (See also Art. 93.) 

■ Polluted water purifies itself not only by oxidation, but 
also by sedimentation, dilution, and the agency of animal and 
vegetable life. 

Organic matter in water forms the food of filth infusoria, 
hydra, rotifera, entomostracan Crustacea, fresh-water shrimp, 
and the larvae of a number of water insects. Entomostraca 
seem to be the most efficient in the purification of streams, 
and thrive on human excrement. A sewage-polluted river may 
contain 25 to 50 or more per gallon; but when the pollution 
becomes intense they seem to disappear, probably because of 
lack of oxygen, but their place is taken by larvae. Diatoms, 
desmids, confervoid algae and other vegetable organisms, to¬ 
gether with bacteria, act largely upon the dissolved impurities; 
although the last-named seem to attack organic matter also. 
These all serve as food for fish; and fish, in turn, for man; 
and sewage matter disposed of by dilution is therefore not 
wasted, although it does not serve as fertilizer for plant life." 

By sedimentation, only the matter in suspension is re- 


DISPOSAL BY DILUTION. 


25 


moved, the proportional amount depending upon the velocity 
and turbulence of motion in the water, the specific gravity and 
size of the matters in suspension, and the time allowed. Sed¬ 
imentation is most active when clay, sand, or other heavy 
matter is carried in the sewage. This, in sinking, carries 
with it other finer and lighter matter, and if there is no motion 
of the water a large percentage of the matter in suspension 
will be deposited. With this will be carried a large number 
of bacteria, many of which, however, will continue to thrive 
in the deposit on the bottom. An illustration of sedimenta¬ 
tion of bacteria is offered by the river Spree, which above 
Berlin has been found to contain 2000 to 20,000 bacteria per 
c.c., below 50,000 to 500,000 (the increase being due to Ber¬ 
lin’s sewage), and below Havel Lake (a lake a few miles below 
Berlin, seven miles long with a slow current through it) 1500 
to 20,000 per c.c. If the water moves with considerable 
velocity, and especially if the bottom be uneven, the sus¬ 
pended matter is carried along and little sedimentation takes 
place. It is doubtful if excessive sedimentation is desirable 
in any body of fresh water or in shallow salt water, since the 
deposit, even in the deepest water, will be worked over by 
bacteria and give off offensive gases, also returning to the 
water much of the organic matter deposited, although in a 
more finely comminuted condition. If the depth be consid¬ 
erable, or the precipitate small in amount, the gases and 
organic matter may be rendered unobjectionable by oxidation 
or otherwise before they reach the surface. 

A large part of the suspended matter does not settle 
under ordinary conditions, but remains on or near the surface 
of the water, with which it mixes. Such intermingling is 
often slow, and the discharge of a sewer can in many cases 
be traced for a long distance as a separate stream, mingling 
but slowly and along its edges with the purer water. For 
this reason discharge should be in a current where possible^ 


26 


SEWERAGE . 


and above rather than below a rapids. The dilution effected 
brings additional oxygen to the organic matter and also makes 
it less apparent, thus decreasing the nuisance; and in salt 
water, or in fresh water where this only is the aim, a sufficient 
dilution may meet the requirements. Authorities differ as to 
the minimum amount of dilution necessary for this purpose, 
but this is usually placed between 1500 and 3500 gallons per 
day per person contributing to the sewage. (The proportion is 
sometimes stated in terms of cubic feet of sewage, but since the 
amount of impurity is not increased by greater per-capita con¬ 
sumption or waste of water, the former method seems prefer¬ 
able.) In the case of the river Exe, it was found, in 1895, 
that the addition of sewage to 40 times its volume of water 
made no serious alteration in the chemical or physical quality 
of the stream. Putrefaction of London’s sewage has been 
arrested by adding to it 35 times its volume of pure water. 
In the Illinois & Michigan Canal, in 1888, sewage was dis¬ 
charged amounting to one-seventh the volume of water flowing. 
For a distance of 29 miles no additional water entered, and 
there was no sedimentation, the current being too swift and 
the bottom being constantly stirred up by boats. During May 
to October about 750 samples were taken at both ends of the 
stretch, from which it was found that the matter in suspension 
was reduced 46$; most of it remaining in solution, however, 
the ammonias being reduced but 14 % and the total solids 8$. 

If the water must be maintained potable, such dilution as 
is above referred to is not sufficient. Since typhoid-fever 
germs have been known to live in ice-water for twenty-five 
days, it is argued that the water of a river receiving sewage 
is dangerous for use as drinking-water for a distance below the 
sewer-mouth covered by the flow of the river during at least 
twenty-five days, or say six hundred miles. Some sanitarians 
maintain that house-sewage should never, or only in very ex¬ 
ceptional cases, be discharged into a stream or lake. The 


DISPOSAL BY DILUTION. 


27 


arguments in favor of their standpoint are certainly weighty, 
but on the other hand the cost of treatment is considerable, and 
many towns could not afford a sewerage system at all if a plant 
for treatment also were necessary. A balance of benefits and 
evils, of what is desirable and what is possible, must be made 
for each case. “ A question which we should be glad to 
have answered is this: To what extent must a polluted liquid 
be diluted in order to be safely used for domestic purposes? 
The answer, however, none can give. We do know this: It 
has been shown by actual experiment that the spores of some 
of the lower orders of vegetable organisms are very difficult to 
deprive of vitality; they may be frozen or heated to the boil¬ 
ing temperature, or they may be kept in a dry condition for 
years, and then, if placed in a favorable medium, become 
active and produce their kind. Admitting the presence of 
disease-germs in a liquid, the liquid may be diluted until the 
chance of taking even a single germ into the system is so 
small that it may be disregarded ; and yet if the prevailing 
theory be true a single germ if taken might produce disas¬ 
trous results. It is easy to push the demands for purity to an 
absurd extent; all reasonable precautions should be taken to 
insure purity, but there is a point beyond which it is foolish 
to attempt to go. In the present state of our knowledge we 
should, however, err on the side of safety, and the mere fact 
that chemical analysis fails to detect impurity should not be 
accepted as a guaranty that a water is fit to drink.” (Nichols, 
“ Water-supply, Chemical and Sanitary.”) 

“Along with our knowledge of the purifying action of 
the minute animals and plants has grown up a more definite 
knowledge of the causation of typhoid fever, cholera, and the 
other water-borne communicable diseases; and before it can 
be positively affirmed that a sewage-polluted stream is safe 
for drinking after a few miles’ flow it must be shown so 
definitely as to be beyond question by those whose special 
studies have fitted them for intelligent judgment that the 


28 


SEWERAGE. 


purifying agencies have practically eliminated the germs of 
the water-borne communicable diseases. Until such showing 
is clearly made the proposition that crude sewage ought not 
to be turned into running streams, ponds, lakes, or other 
bodies of water which either are or may be the sources of 
water-supplies must be considered as holding good.” (Rafter 
and Baker, ‘‘ Sewage Disposal in the United States.”) 

The above restrictions apply equally to ice which may be 
used for drinking-water, since it is known that bacteria are 
not wholly excluded from water by freezing, and that many 
varieties will live in ice for months. 

The discharging of sewage into tidal waters involves the 
principles given as applying to discharge into rivers so far as 
creating a nuisance is concerned, and also the practical con¬ 
sideration of the movements of prevailing winds and tides. 
“ In every case the outfall of the discharging sewer should be 
below the level of the water at all states of the tide, and be 
provided with a tidal valve, to prevent the ingress of sea-water. 
The position of the outfall should, if possible, be so chosen 
that the sewage will be always carried out to sea independently 
of the tides, and the possibility of its return avoided ; and for 
this purpose advantage should be taken of any current that 
flows off or along the shore, the sewage being discharged into 
it, and thus carried away from the neighborhood of the town. 
If there is a current setting along the shore, then the sewer- 
outfall should be placed at that extremity of the town which 
will prevent the sewage being borne along the whole sea-front. 
The prevailing winds also must be taken into account, so that 
floating matters may not be blown back toward the town.” 
(W. H. Corfield, “Treatment and Utilization of Sewage.” 

From experiments conducted by the Metropolitan Sewer¬ 
age Commission in 1898 in Boston Harbor, it was concluded, 
in the case of the Moon Island outlet, where sewage is stored 
and discharged on the ebb~tiH^ and in addition about the same 


DISPOSAL BY DILUTION. 


2 9 


amount is discharged continuously, that the area covered by a 
reservoir-discharge in three-quarters of an hour of 22,000,000 
gallons is approximately 750 acres; when but 11,000,000 gal¬ 
lons is discharged at once this area is not more than 250 acres. 
In calm weather the sewage is offensively visible over two- 
thirds of this area, but the odors are confined to a relatively 
small portion. By far the greatest amount of sewage is found 
in the upper two or three inches of the polluted area, and this 
largely disappears in two or more hours after the discharge, 
depending chiefly upon the force of the waves. A thin film of 
grease sometimes covers large areas, but is not accompanied 
by enough sewage to be detected. Within the polluted area 
sewage cannot be detected at a greater depth than 5 feet at 
the outlet and 2 feet near the edges of the area. When 
35,000,000 to 40,000,000 gallons daily is continuously dis¬ 
charged the dilution is such that fifteen minutes after leaving 
the outlet, sewage constituted but 20 per cent of the surface 
water; 30 minutes after, 15 per cent; 45 minutes after, 5 per 
cent; and 60 minutes from the outlet but 4 per cent of the 
surface-water was sewage. The discoloration was evident for 
about i-J miles, and covered about 350 acres during ebb-tide 
and 300 acres during flood-tide. 

Shores within one-half to one mile of sewer-outlets are 
apt to be polluted, and these outlets should hence be at some 
distance from any land, when possible. 

It should be remembered that the water of dilution has 
been considered in the above discussion to be unpolluted; 
and that the same water swinging back and forth with the 
tide past a sewer-outlet will soon become grossly polluted. 
The actual dilution will be closely indicated by multiplying 
the actual cross-sectional area of the channel by the distance 
separating the positions occupied by a given sub-surface float 
at two successive ebb-tides, as compared with the sewage dis¬ 
charged in the same time. 


CHAPTER III. 




AMOUNT OF SEWAGE. 

Art. 13. Sewerage Conduits. 

The object of a system of sewers is in general to conduct 
all excreta and fouled waters from the places of their origin 
to an appointed outlet, and as rapidly and continuously as 
possible. No part of the sewage should be retained in any 
portion of the system for any considerable time, either in its 

s 

liquid form or in the shape of deposits upon the bottoms or 
walls of the conduits or their appurtenances; for such reten¬ 
tion may permit of putrescence of the organic matter before 
it reaches the place assigned for disposal, the conduits thus 
becoming no better than “ elongated cesspools.” The insur¬ 
ing of this result with the greatest certainty and economy is 
the prime requisite in the design of a sewerage system. 

The largest part of the system is made up of conduits of 
various size, shape, grade, material, and depth below the 
ground-surface. The two last are practical points to be con¬ 
sidered later (Articles 37 and 45), but the size, shape, and 
grade are to be determined—approximately at least—by 
theoretical considerations. The data used in these considera¬ 
tions are (1) the amount and character of the sewage to be 
removed, and (2) the relative surface elevations and grades 
along the line of the proposed sewer-conduit. The latter 
are obtained by the instrumental field-work, to be discussed 
in Chapter VI. While the grade of the sewer need not be 


% 


30 


AMOUNT OF SEWAGE . 


31 


that of the street-surface, it cannot depart far from this with¬ 
out greatly increasing the difficulty and cost of construction. 
The two grades will therefore be approximately parallel 
unless very good reasons to the contrary exist. 

Art. 14. Amount of House-sewage. 

The obtaining of satisfactory figures for the amount of 
sewage is one of the most difficult tasks entering into the 
designing of a system. The sewage to be considered is of 
two entirely different kinds, from two totally different 
sources: house-sewage from dwellings, stores, factories, and 
other buildings, and storm-water from the streets, the ground- 
surface, and from roofs. The former is limited in quantity 
largely by the number of inhabitants and industrial establish¬ 
ments and the water contributed to the sewers by each. 
The latter is limited by nature’s local limit of intensity of 
rainfall, the area tributary to the sewer, and the proportional 
run-off. 

Considering first the house-sewage, this is almost entirely 
composed of water which has first been introduced artificially 
into the dwellings or establishments. Excreta and solids 
legitimately finding their way to the sewer comprise only a 
very small part of the sewage—from 5 to 15 parts in 10,000. 
There may be besides this comparatively small amounts of 
leakage of ground-water, roof-water, and flushing-water 
reaching the sewer. It would seem, therefore, that we may 
make a close approximation to the amount of house-sewage 
by using the water-consumption of the town in question. 
This can usually be obtained from the pumping records, or, 
in the case of a gravity supply, from a meter set in the main 
near the reservoir. Table No. 1 shows the rates for a num¬ 
ber of cities of the United States at intervals of 10 years. 
This table shows the great difference between the per capita 


32 


SEWERAGE. 


Table No. 1. 


Cities. 



Population. 


rt c 
o 

rt O. 

u a 
»- 5 

£ c 
P" o 

U 


Population. 


u a 

5 

U 


Population. 


c< r* 

u a 

£l 

P" o 
U 


New York City ... 
Chicago, Ill. .... 
Philadelphia, Pa.. 
Brooklyn, N. Y.. 

St. Louis, Mo. 

Boston, Mass. 

Cincinnati, O. 

Cleveland, O. 

Buffalo, N. Y. 

Detroit, Mich. 

Louisville, Ky.... 

Columbus, O. 

Paterson, N. J.... 
Fall River, Mass.. 
Cambridge, Mass . 

Troy, N. Y. 

Des Moines, la... 

Erie, Pa. 

Terre Haute, Ind. 
Wilmington, N. C 

San Jose, Cal. 

Keokuk. Ia. 

Brookline, Mass.. 
Baton Rouge, La. 
Nanticoke, Pa.. .. 


942,292 
298,977 
674,022 
396,099 
310,864 
250,526 
216,236 
92,829 
II7.7I4 
79'. 5 77 
100,753 


90.2 
62 32 
55 -ii 
47.16 

35-38 

60.15 

40.0 

33.24 
58.08 

64.24 
29.0 


1,206,590 

503.304 

847,542 

566,689 

346,000 

416,000 

256,708 


78.7 

114.0 

68.1 

54-2 

72.1 
92.0 
75-9 


. 65.0 

.. 106 o 

118,000 152.0 

. 52 o 


49,430 30.1 


1,515,301 
1,099 850 
1,046,964 
806,343 
45L770 
448,477 
296,908 
261,353 
255,664 
205,876 
161,129 
88,150 
7S.347 
74,39S 
70,028 
60,956 
50,093 
40,634 
30,217 
20,056 
18,060 
14,101 
12,103 
10 478 
10,044 


79 
138 

131 

72 

72 

80 
112 
103 
186 
161 

74 

78 

128 

29 

64 

125 

55 

112 

83 

22 

194 

78 

73 
19 

T 99 


rates in different cities. It also shows in each city an increase 
of from 10$ to 100% in consumption during each decade. 
Neither the increase of per capita consumption nor the dif¬ 
ference in rates of increase in the various cities seems to 
follow any law, except that the former shows a constant 
advance. It might be expected that the per capita con¬ 
sumption would be greater in cities where there was consider¬ 
able manufacturing or many well-kept lawns than where these 
conditions did not exist; and this is the general rule—with 
many exceptions, however. Also large cities usually have a 
higher rate than small ones; but this rule also has many 
exceptions. 

















































AMOUNT OF SE WAGE. 


33 


For each particular case the daily consumption should be 
obtained from the water-works record, or, if there are no 
records of consumption for that locality, a careful selection 
should be made of the per capita consumption of a city whose 
conditions closely resemble those of the place in question. 
From these the per capita rate will be obtained. In order to 
be on the safe side the present rate should be increased by at 
least 25 f 0 to allow for a probable increase in consumption, 
since the construction must serve not only the present popu¬ 
lation, but that of the next 30 or more years. 

If meters are used on a majority of the services a great 
reduction in the consumption can be effected—from 30$ to 
6 o </ 0 in most instances. 

Unless water-meters have become generally established 
and accepted, however, no allowance should be made for the 
reduction in sewage due to their use unless the average daily 
rate exceeds 100 gallons per capita. There is no reason for 
a daily rate exceeding this amount, and the present tendency 
is to meter supplies before they reach this point. An allow¬ 
ance of 100 gallons will be made in calculations in this work, 
as being a safe one for any but exceptional cases. 

The average daily consumption, however, “ is not uniform 
throughout the year, but at times is greatly in excess of the 
average for the year and at other times falls below it. It 
may be 20% or 30$ in excess during several consecutive 
weeks, 50 <f> during several consecutive days, and not infre¬ 
quently 100$ in excess during several consecutive hours.” 
(J. T. Fanning, “ Water Supply Engineering. ”) Many water¬ 
works engineers use 75$ excess as an average. This gives 
for a maximum flow, on a basis of 100 gallons daily, a rate 
of 175 gallons per capita daily = .1215 gallons per minute = 
.00027 cubic feet per second. 

It must be most urgently insisted, however, that each case 
should be studied by itself in the light of all the data avail- 


34 


SE WEE A GE. 


able. These figures are given as approximate averages only, 
to be used in designing when no local records exist. It 
should also be borne in mind that the consumption given is 
an average including that used in manufacturing and for all 
other purposes. These last constitute a very uncertain por¬ 
tion of the whole, but unless there were definite figures 
obtainable it would not be safe to reduce the average by 
more than 10$ to obtain a rate for residences only. As the 
assumed maximum rate—175 gallons—was but a roughly 
estimated average, it may be used unchanged for residential 
districts; and where factories are to be provided for a study 
should be made of the processes employed in them in order 
that a close approximation may be made to the amount of 
sewage to be expected from each. 

The amount of house-sewage from buildings (other than 
waste water from factories and water-motors) which will reach 
any particular sewer will depend almost wholly upon the 
number of persons contributing to this amount. For a 
district or city this number may be obtained in two ways 
—by estimating the ultimate number of residences and 
assigning a certain number of occupants to each, doing the 
same with factories, stores, and other buildings; or by 
estimating the probable ultimate population per acre for 
different sections of the city. The former is the more accu¬ 
rate for built-up sections; the latter sufficiently so for 
undeveloped territory or that which will probably undergo a 
change in the character of its buildings. 

For use in calculating by the first method the following 
table adapted from the U. S. census of 1880 is given.* 

There are in each city certain districts in which the 
population is much more dense than is indicated by this 
table. One hundred persons in one dwelling is not an excep¬ 
tional rate in certain portions of New York City. For an 
ordinary residence district six persons to each dwelling is a 


* See also Table No. 31 , page 430*-. 




AMOUNT OF SEWAGE . 


35 


Table No. 2 . 


Cities. 

Population. 

Persons in a 
Family. 

Persons in a 
Dwelling. 

New York City. 

1,206,299 

4.96 

16.37 

New Orleans, La. 

216,090 

4-77 

5-95 

Providence, R. I. 

104,857 

4-52 

7.41 

Kansas City, Mo.. 

55,785 

5-97 

6.48 

Nashville, Tenn. 

43,350 

5-09 

6.13 

Denver, Colo. 

35,629 

5-99 

6-75 

Harrisburg, Pa. 

30,762 

4.78 

5.16 

Erie, Pa. 

27.737 

5-24 

5-66 

Des Moines, la. 

22,408 

5.14 

5-37 

Sacramento, Cal. 

21,420 

4 . 5 i 

5-07 

Springfield, Ill. 

I 9>743 

5.04 

5.60 


sufficient average. In factories and stores which do not use 
water for manufacturing purposes the maximum hourly rate 
per capita of occupants is not nearly as great as in the case of 
residences; a maximum rate of 20 gallons per day will be 
sufficient allowance for ordinary cases, being contributed by 
water-closet flushes, urinals, and wash-basins. One person 
to each 50 square feet of floor-space may be taken as a 
maximum density for factories, and one to each 75 square 
feet for office-buildings. 

A method frequently used is that of adding a percentage 
of increase to the present population of each city or section. 
American towns under 50,000 population have been found as 
a general rule to double in size in about 15 or 20 years. 
Having ascertained for each case its past rate of increase and 
present population, these are taken as the basis for calcula¬ 
tions. But this increase is far from uniform over the entire 
area of a town, differing in different sections; also after a 
section has reached a certain density of population it remains 
practically stationary, unless its character change—as from 
residential to business or manufacturing. The percentage of 
total growth of a town may be used, however, as a check 
upon the sum of the populations assumed for the various sec¬ 
tions. The law of increase varies in different cities, but that 























3 ^ 


SE WEE A GE. 


followed in the past by the one under consideration having 
been obtained from the records can be projected into the 
future, it being assumed that this law will remain constant 
(see Art. 129). 

Considerable judgment must be used in locating division¬ 
lines between sections and assigning to each its density of 
ultimate population. The most hilly sections will probably 
be least thickly, and those in the level bottom lands most 
thickly, populated. Further than this it would be unsafe to 
try to state any general law. The least population which 
should be assigned to any habitable section within city limits 
is 20 per acre. The per acre population in any residence 
section can be expressed by the equation 

' 43560/^ 

fd\lb + w(l -}-£+«/)]’ 


in which / = the average length of a city block; 

breadth “ “ “ “ 

number of occupants of each lot; 

front feet to a lot; 
depth of a lot; 
width of a street; 
population per acre. 

For a section where the blocks are 400 ft. by 200 ft., 
streets 66 ft. wide, lots 50 ft. by 100 ft., and the population 
residential (0 — 6), 


b = 

0 — 

/= 
d = 

W = 

P = 


< ( 


1 < 


i < 


t ( 


< i 


t ( 


p — 43560 X 400 X 200 X 6 

“ 50 X 100[400 X 200 + 66(400 + 200 + 66)] 


= 34 ±- 


For a tenement district, each building on a lot 50 ft. by 
100 ft. and containing on an average 80 occupants, A* would 
equal 453, which is about P for the Tenth Ward, New York 
City. 

A block with lots 25 feet by 80 feet and with 6 occu¬ 
pants each represents fairly well the most dense residence 






A MO UNT OF SEWAGE. 


3 7 


section of an average city of 10,000 to 100,000 population. 
This gives P= 85. In many cities the maximum does not 
exceed 50 per acre. 

The population found times .00027 f° r residences and 
times .00003 f° r factories and office-buildings (on the basis of 
the previously assumed daily consumption) will give in cubic 
feet per second the maximum amount of house-sewage from 
buildings to be expected. To this must be added manufac¬ 
turing wastes, which are to be allowed for in quantities which 
must be decided upon separately for each individual case. 
Also if the soil is inclined to be wet at a depth less than that 
of the proposed sewer (and this includes a larger proportion 
of localities than most persons realize) an additional allowance 
must be made for ground-water leaking through the joints 
(see Art. 35). With care this need not amount to more than 
one cubic foot per second for each 30 to 100 miles of sewer; 
but it has been known under most unusual conditions to more 
than equal the entire capacity of the system.* 

Where flush-tanks are used (see Chapter V) an additional 
allowance is frequently made for water from them. But this 
seems entirely unnecessary, since their very purpose is to tem¬ 
porarily gorge the sewer for as great a distance as possible; 
and the smaller the sewer the better is this mission fulfilled. 
The average discharge per minute of 100 tanks, each dis¬ 
charging 300 gallons once in 24 hours, would amount to only 
1 ±<f 0 of the capacity of a 15-inch sewer at minimum grade. 

Art. 15. Data of House-sewage Flow. 

Instead of using rates of water-consumption as equivalent 
to the sewage discharge it would undoubtedly be preferable 
to establish the actual relation between these, based upon the 
rate of flow of sewage itself in various towns already sewered. 
But very few such records exist—too few to enable us to 
deduce a definite law from them with certainty, although a 

* Average leakage of 137 miles of 8 in. to 36 in. in Boston, .00 cu. ft. per 
sec. per mile. Double this in the spring. 





38 


SEWERAGE. 


study of even these few is instructive. Probably the most 
extended series of gaugings of sewage discharge made in 
America are those of the Providence, R. I., sewers by 
Samuel M. Gray. A condensed summary of them and of 
other gaugings is given in the following tables: 

Table No. 3 . 

SUMMARY OF RESULTS OF WEIR MEASUREMENTS OF SEWAGE FLOW 

IN PROVIDENCE, R. I. 

(Condensed from a Report by Samuel M. Gray on the Sewerage of Providence.) 


Street. 

Houses 

Connected. 

Population 

Connected. 

Dorrance. 

772 

575 

6562 

4480 

Rrook. 

« 4 

a 



a 



44 



i 4 



Elm. 

1114 

8800 

4 4 

4 4 



4 4 



4 4 



N. Main. 



4 4 



4 ( 



Blackstone.. . . 



4 4 


* 

4 4 



4 4 



4 4 



Ives. 

44 

204 

1814 

4 4 



4 4 



College... 

108 

824 

4 4 

Point. 

321 

31 

2729 

239 

Power. 

44 

4 4 



Nash. 

25 

193 

4 4 

4 4 



Park. 

21 

162 

44 

Martin. 

153 

86 

II78 

655 

Pitman. 

4 4 





Average 

Maximum 


Discharge 
per Second. 

Discharge 
per Second. 

Measurement. 

7.32 

II.65 

( Average of 
} May and June 

5.92 

6.78 

Sat., Feb. 2 

5.61 

6.78 

Mon., “ 4 

3-985 

5 47 

Tues., July 1 

3-88 

5-47 

Thurs., “ 3 

3-86 

5-76 

Sat., “ 5 

4.28 

5-47 

Mon., “ 7 

4.15 

7.90 

Jan. 28 

3.69 

7.90 

Tues., “ 29 

3-317 

6.32 

Wed., June 4 

3 37 

6.32 

Fri., “ 6 

3.10 

5.11 

Thurs., “ 19 

2-57 

4-45 

Mon., May 12 

2.46 

3.80 

Wed., “ 7 

1.76 

3-25 

Fri., July 25 

1.50 

3-20 

Mon., Feb. 11 

2.40 

5-40 

Thurs., “ 14 

2.30 

4.82 

Sat., “ 16 

2.06 

2.65 

Mon., “ 18 

2.106 

3.20 

Fri., “ 29 

0-753 

1.02 

Mon., March 3 

0.854 

1.3S 

Wed., “ 5 

0.695 

1.30 

Mon., Aug. 25 

0.600 

0.92 

Wed., “ 27 

1.05 

1.82 

Fri., May 2 

1.07 

1.81 

Mon., “ 5 

i -57 

3.82 

j Mean for May 
} 6-21 

0.26 

0.56 

Wed., April 23 

0.26 

0.54 

Fri., “ 25 

0.045 

0.14 

“ Aug. 22 

0.037 

0.135 

Mon., April 21 

0.030 

0.060 

Tues., “ 22 

0.036 

0.086 

Aug. 6, 7, 11 

0.034 

0.187 

Fri., April 18 

0.043 

0.385 

Mon., Aug. 18 

1.208 

1.400 

Wed., July 9 

1.202 

2.380 

Mon., April 28 

0.744 

1.380 

Wed., “ 30 
























































AMOUNT OF SEWAGE. 


39 


Table No. 4 . 

GAUGINGS MADE IN TORONTO, CANADA, IN THE SPRING OF 1891, 

LASTING THREE DAYS. 


Popula¬ 
tion per 
Acre. 

Total 

Popu¬ 

lation. 

Discharge. 
Gallons per 
Head per 
Day. 

Popula¬ 
tion per 
Acre. 

Total 

Popu¬ 

lation. 

Discharge 
Gallons per 
Head per 
Day. 

Popula¬ 
tion per 
Acre. 

Total 

Popu¬ 

lation. 

Discharge. 
Gallons per 
Head per 
Day. 

15-7 

39,014 

77 

17.6 

6,160 

IOI 

41.7 

II, 30 C 

68 

46.2 

17,186 

133 

42 3 

11,125 

69 

9.4 

7.238 

105 

8.8 

3.168 

83 

39-8 

6,368 

113 

45-7 

14.213 

89 

44.0 

572 

316* 

42.4 

8,26S 

89 

38.3 

19,265 

53 

45-5 

4-595 

77 

11. 8 

8,732 

102 

24.O 


87 

41.8 

1.045 

113 

43-7 

9,832 

89 





* No explanation given for this high average. 

Table No. 5 . 


GAUGINGS MADE IN SCHENECTADY, N. Y., WEDNESDAY, FEBRUARY 5, 
AND THURSDAY, FEBRUARY 6, 1892 — HOURLY FOR 24 HOURS. 

(Fifteen miles of sewers, about 1500 house-connections tributary to the point 
where gaugings were made. Before house-connections were made a seepage 
of 60,000 gallons per day was measured. There was also 50,000 gallons of 
water contributed daily by flush-tanks. These two, or 110,000 gallons per day, 
have been deducted from the total hourly flow in obtaining the quantities in the 
table.) 

WEDNESDAY, FEBRUARY 5, 1892. 


Hour . 

Total flow per hour . . 

9 A.M. 
35,217 

IO 

38,769 

11 

32,892 

12 M. 
32,892 

I P.M. 

34,049 

2 

35,217 

3 

36,490 

4 

34-049 

Hour. 

Total flow per hour . . 

5 P.M. 

32,S92 

6 

31,840 

7 

31,840 

8 

31,840 

9 

29,301 

10 

29,301 

11 

29,301 

12 

28,135 

THURSDAY, FEBRUARY 6. 

Hour. 

Total flow per hour ... 

I A M. 
28,135 

2 

28,135 

3 

25,711 

4 

28.135 

5 I 6 | 7 

26.833 26,833 29,461 

8 

31,840 


Average flow per hour, 31,213 gallons; minimum flow, 25,711 gallons; max¬ 
imum flow, 38,769 gallons, or 24$ increase over the average. 


Table No. C. 

WATER-CONSUMPTION AND SEWAGE FLOW, ATLANTIC CITY, N. J.> 


DECEMBER, I 89 I-NOVEMBER, 1892. 

(Average Daily Percentage of Excess of Water Consumed over Sewage 

Pumped—by Months.) 


December. 

January. 

February. 

March. 

April. 

etf 

2 

June. 

1 

A 

p 
. —> 

August. 

• 

September. 

October. 

i 

« 

November. 

32 

50 

37 

Excess 

- 

O 

—►» Ln 

1 

54 

iter-ta] 

61 

ps ove 

64 

r sewe 

36 

r r arm 

11 

“otiom 

36 

perr< 

75 ! 66 
?ntaee . 

CO 00 

*-< cn 


The average daily percentage »»i excess for the year := 45$. 
The average excess of water-taps for the year = 44#. 






























































































4 ° 


SEWERAGE. 


Table No. 7 . 

HESULT OF A GAUGING BY WEIR MEASUREMENT OF THE FLOW OF 
THE MAIN OUTFALL SEWER OF THE STATE INSANE HOSPITAL 
AT WESTON, W. VA., IN JANUARY, 1891. 

(Made by Geo. W. Rafter. Condensed from “Sewage Disposal in the 
United States.” Self-closing fixtures were used in the building. 10,000 gallons 
per day, or 7 gallons per minute, of water of condensation from the steam¬ 
heating apparatus was discharged into the sewer.) 




Rate in 



Rate in 



Rate in 



Rate in 

Day. 

Hour. 

Gallons 

Day. 

Hour. 

Gallons 

Day. 

Hour. 

Gallons 

Day. 

Hour. 

Gallons 


per Min. 


per Min. 


per Min. 


per Min 


12 

78 75 


I A M. 

44-55 


I P.M. 

99-45 


I A.M. 

34 65 


I P.M 

93.60 


2 

44-55 


2 

86.40 


2 

34.65 


2 

93.60 


3 

44-55 


3 

93.60 


3 

39.60 


3 

75.60 


4 

44-55 


4 

75.60 


4 

49-05 

• 

4 

75.60 


5 

49-05 


5 

93.60 


5 

49-05 

aj 

5 

70.20 


6 

64.80 

"O 

C/7 

i-, 

6 

81.00 


6 

58.50 

c n 

6 

75.60 

C/7 

u 

7 

75.60 

7 

93-00 


7 

70.20 

D 

C 

TD 

1) 

7 

8 

75 60 
70.20 

3 

_C 

H 

8 

9 

86.40 

105.30 

3 

rC 

H 

8 

9 

58.50 

53-55 

Frid 

8 

9 

86.40 

105.30 

£ 

9 

58.50 


10 

117.90 


10 

53-55 


10 

86.40 


10 

5?-55 


11 

93.60 


11 

44-55 


11 

86.40 


11 

44-55 


12 

93.60 


12 

44-55 


12 

105.30 


12 

44-55 











The flow of the Compton Avenue sewer, St. Louis, Mo., 
was gauged hourly from March 15 to 23, 1880. The mini¬ 
mum flow measured was 88 gallons per minute, the maximum 
203 gallons, and the mean 132 gallons. 

A gauging of the College Street sewer, Burlington, Vt., 
taken at 15-minute intervals from 7.30 A.M. to 10.30 P.M. 
gave two maximums, one at 7.45 A.M., the other at 9 A.M.; 
these were each 140 gallons per minute. The minimum flow 
was 65 gallons, the mean 115 gallons. Fifty-four houses 
were connected; the tributary population was 325. 

Gaugings made at Memphis, Tenn., for one day gave a 
maximum of 80 gallons and a minimum of 35 gallons per 
minute. 

Gaugings made at Kalamazoo, Mich., in 1885, from 
1 A.M to 12 midnight on Monday, March 9, gave a minimum 































AMOUNT OF SEWAGE, 


4 * 


Plate No. I. 


4 , 000,000 

3 , 000,000 

2,000,000 

1,000,000 


4 , 000,000 

3 , 000,000 

2 , 000,000 

1,000,000 


4 , 000,000 

3 , 000,000 

2,000,000 

1 , 000,000 


5 , 000,000 

4 , 000,000 

3 , 000,000 

2,000,000 

1,000,000 


5 , 000,000 
4 , 000,000 
3 , 000,000 
2,000,000 
1,000,000b 



• EAST SIDE SEWER 
■ WEST “ “ 

BOTH SEWERS COMBINED 
WATER CONSUMPTION 













































































































































































































































































































































































































































































































































































42 


SEWERAGE. 


flow of 224 gallons per minute, a maximum of 287 gallons, 
and a mean of 254 gallons. 

Gaugings were made at Des Moines, Iowa, from June 30 
to July 16, 1895, by J. A. Moore and W. J. Thomas, class 
of ’95, Iowa Agricultural College (see Plate I). The sewerage 
system at the outlet of which the gaugings were taken com¬ 
prised: on the west side 235,000 feet of sewers, contribu- 
tary population 19,400, 15 hydraulic elevators; on the east 
side 29,000 feet of sewers, contributary population 8100, 3 
hydraulic elevators. 

These were combined sewers. Rain fell on two Sundays 

* 

only, and is indicated by the unusual height of the curve. 
Water-meters were used on the services; water was supplied 
to 33,700 persons, but the amount consumed by each was 
not ascertained, the average consumption for the city being 
taken. The diagram for the west side shows noon-hour stops 
of factories. The high-water curves for July 10, 11, 12, and 
13 were caused by the water company flushing dead-ends 
outside of the limits of the sewers gauged. On the 12th the 
large flow in the west-side sewer was probably caused by a 
part of this flushing-water reaching it. 

The maximum dry-weather rate of flow on the west side 
was at 10.15 A.M. Friday, July 12 — 175.3 gallons per capita. 

The maximum dry-weather rate of flow on the east side 
was at 6.30 P.M. Tuesday, July 2 —142 gallons per capita. 

The minimum dry-weather rate of flow on the west side 
occurred at 4 A.M. Saturday, July 6—23.2 gallons per capita. 

The minimum dry-weather rate of flow on the east side 
occurred at 4.30 A.M. Friday July 5—22.5 gallons per capita. 

The average dry-weather rate of flow on the west side was 
66 gallons per capita. 

The average dry-weather rate of flow on the east side was 
74 gallons per capita. 

Table No. 8 gives the water pumped and the sewage dis- 



AMOUNT OF SEWAGE. 


43 


Table No. 8 . 


Date. 

Water. 

Sewage. 

81.6# of the 
Water Pumped. 

Remarks. 

July 3 

2,720.000 

2,200,000 

2,219,520 


“ 4 

1,829 000 

1,330,000 

1,492,464 

Holiday 

“ 5 

2 . 352,635 

2,050,000 

I» 9 x 9 i 7 50 


“ 6 

2,750,205 

2,040,000 

2.244,167 


“ 7 

1,809,110 

1,115,000 

1 , 476,234 

Sunday; rain 

“ 8 

2,379,820 

2,030,000 

I, 94 L 933 


“ 9 

2 , 437,325 

2,020,000 

1,989,265 



charged during the seven days when the measurements taken 
were apparently reliable. The first column gives the total 
amount of water pumped; the second, the total sewage flow; 
the third, 81.6# of the first column, that being the proportion 
between the number of water-taps and that of the sewer-con¬ 
nections. The close correspondence between the two last 
columns shows what an excellent index the water-consump¬ 
tion furnishes, in this town at least, of the total house-sewage 
to be expected. July 12 was the only date when the maxi¬ 
mum flow of the west side exceeded 125 gallons per capita, 
and then for two hours only. The average for this side was 
66 gallons. Disregarding the maximum of the 12th instant, 
which was due to hydrant-flushing, we have a maximum for 
this side 89^ greater than the average; and for the east side 
the maximum was 92$ above the average. The record, 
however, covers two holidays out of the seven, making the 
average unusually low; also the general average for that time 
of year would ordinarily be lower than that for an entire year. 

It is thought that these include all the published records 
of gaugings of sewage flow which have been made in this 
country. They seem to point uniformly to the conclusions 
already stated—that the winter flow of sewage is greater than 
the summer; that the maximum and minimum flow do not 
ordinarily vary from the yearly average more than 75$, but 
frequently do by 50 <f 0 \ that the house-sewage per capita very 
nearly equals the water-consumption where the taps and sewer- 
connections are equal in number. 
















44 


SEWERAGE. 


The engineer must select and use with a great deal of 
judgment all the data obtainable in fixing upon the quantities 
which the sewer should be designed to carry. The method 
of making the calculations will be explained more at length 
in Chapter VII. 

Art. 16. Amount of Storm-water. 

The amount of storm-water reaching a given sewer 
depends upon the rate of rainfall, the time during which this 
rate is continued, the proportion of the rainfall which flows 
off, and the time taken by a raindrop after falling to reach 
the point under consideration. This last depends upon the 
shape, extent, and nature of the surface over which, and the 
length and grade of the sewer through which, it must flow. 

Art. 17. Rates of Rainfall. 

It is apparent that the rate at which the water reaches the 
sewer depends to a greater or less degree on the rates of rain¬ 
fall from minute to minute, and not upon the amount falling 
in a day or even in an hour. Records giving rainfalls for 
these latter units of time are, therefore, valueless to the 
sewerage engineer. It is only within recent years that gauges 
have been used which automatically register the rate of rain¬ 
fall at each moment of a storm. But so great a necessity for 
such records has been felt that the use of self-registering rain- 
gauges is becoming more and more general, and in most of 
the large cities continuous record of the rates of rainfall is 
obtained either by a city department or by the United States 
Weather Bureau. 

Since the maximum amount of water to be removed 
determines the size of the sewer, we are concerned only with 
the maximum rates or those near the maximum. Rates of 
heavy rainfalls for various cities of the United States are 


9 


AMOUNT OF SEWAGE. 45 

given in Table No. 9. Where possible several high rates 
during the same or consecutive years are given for each 
locality, but no attempt has been made to give a record of 
all severe storms for any one place or year. An examination 
of rainfall data covering many years shows that in New 
England a rate of 3.6 inches an hour continuing for 5 minutes 
may be expected every year or two, a rate of 2 inches con¬ 
tinuing for 20 minutes, a 1.5-inch rate continuing for* 30 
minutes, and 1 inch in 60 minutes. In New York State 
the rate may be about 20 % and in Pennsylvania about 30$ 
higher. In Baltimore and Washington we may expect a 
5-inch rate for 5 minutes, a 4-inch rate for 10 minutes, a 
2.7-inch rate for 20 minutes, a 2-inch rate for 30 minutes, 
and 1.4 inches in 60 minutes. In New Orleans a 5.5-inch 

rate for 5 minutes, a 4.5-inch rate for 10 minutes, a 3-inch 

rate for 20 minutes, a 2.5-inch rate for 30 minutes, a 2-inch 

rate for 60 minutes or even more may be expected. In the 

central States a rate of 3.7 inches for 10 minutes, 2.8 inches 
for 20 minutes, 2.3 inches for 30 minutes, and 1.7 inches in 
60 minutes may be expected. Further data, however, may 
require a change in any of these values. 

The last rates in the table are given to show what down¬ 
pours sometimes occur in certain sections. In 2 hours 
there fell at St. Kitts more than 12 inches; how much more 
could not be ascertained. The Palmetto gauge was swept 
away after registering 12 inches in 2 hours. 

The records seem to show, where any information on the 
subject is given, that the maximum intensity usually lasts 
but a few minutes, seldom more than ten; that it sometimes 
occurs at the beginning of a storm, but in a great majority of 
instances occurs at the middle or end of it, quite a number 
stopping 10 to 20 minutes after the maximum rate is 
attained. As to the area simultaneously covered by the 
maximum rates of fall, almost no data are available. 


4 6 


SEWERAGE. 


Table No. 9. 

MAXIMUM AMOUNTS OF RAIN FALLING DURING DIFFERENT PERIOD 5 

OF TIME. 


Length of Period in Minutes. 


5 

to 

15 

20 

25 

30 

45 

60 

Over 60. 

Amt. 

Dura¬ 

tion. 








0.50 

5.20 

24 h. 

.... 

1.40 

.... 

1.50 

1.30 






















0.50 

1.50 




















2.56 

. 

.. .. 



0.75 





.... 

0.90 





1 - 74 - 








5-°3 
‘•73 
1.18 

h. 

h. 

2 h. 












0.50 





o *35 

t • • • 

• • • • 






1.40 

I .20 
O.80 
O.60 








.... 

1.30 

.... 

1.50 















3.60 
6.17 

24 h. 
24 h. 












0.80 




I .OO 




2.60 





0.25 

I .OO 

I .OO 

I .OO 
0.80 
0.60 
0.40 








1.28 

x.50 
1.60 
1.30 

.... 

o -45 
















1.00 
0.96 
0.64 












0.46 

0.85 

0.58 

O.92 

0.62 
o -95 

0.83 

o -95 



JJ 



0.80 

0.52 

0.50 

0.40 

0.40 

0.60 

0.23 

°-35 

0.14 
0.30 
0.07 
0 10 

0.30 

I 60 
O.80 
O.60 

O.85 

0.70 

0.75 

I .20 
0.60 

2.00 

1.50 

.... 

. 



.... 

I .30 

.... 







o -75 

1.20 

1.00 

1.20 

1.50 

1.00 

1.48 
1.32 
1.82 
i -75 
1.17 

1.78 

i lei 

1 -95 
2.00 

‘•25 

2.0«5 

1.87 

2 - I 5 
2.10 

2.00 
2.70 
2.62 

2.45 

2.20 




3 - 4 ° 

3-‘9 

2.70 

2.32 

6.00 

3 - 3 ° 

2 h. 

2 h. 

2-35 

ii h. 


4.12 
1.78 

1.71 

I * I 5 

x.50 

0.88 

1.10 

3.60 

1.88 

1.99 

1.80 



0.65 

0.20 

0.61 

0.26 

0.30 

°-45 
i .00 

0.80 

0.60 

0.90 

0.47 

0.70 

0.44 

o -37 

0.57 

‘•‘5 

0.85 

0.92 

0.77 

0.47 

0.65 

I .4O 

O.9O 

1 • 3 ° 
0.82 
0.62 
0.77 

*•55 

1 01 

i -57 

0.91 

o -75 

0.90 









I .OO 

1.23 



. 

. 

















1.10 

0.88 

0.49 

0.85 

0.63 

o -75 

0.46 






‘•75 
3 - 3 ° 

2 h. 

2 h. 

0.28 
0.04 
0.15 
0.38 
0.25 
0.06 
0-35 

0.58 
0.19 
o -45 
o -57 
0.50 
o -33 






i *3 
0.79 
x .00 
0.91 
0-95 
0.60 

1.23 
1.04 

1 .07 

1 • ‘3 

0.99 

0.66 

1.38 

1 - 3 1 
1.14 
1.30 
1.02 
0.70 



‘•73 







I .70 

1.78 





0.79 

0.91 

0.82 

11. 5 + 
8.8 

. 

. 







.... 

... 

... 

-•• 

•• 

.... 

.... 



36 -h 
12 + 

24 h. 

2 h. 


















Place and Date. 


Boston, Oct. 12, T895 

»c j-1879-1891 

“ July 18, T884 
Providence, R. I., May 18, 1877 
“ “ Aug. 29, 1877 

“ “ “ 6, 1878 

“ “ 28, 1882 

Ithaca, N. Y., Aug. 4, 1892. Preceded by 
5 hours of light rain 
Mt. Carmel, N. Y., July 2, 1897 
Morrisania, Oct. 30, 1866 
New York City, Sept. 19, 1894 

“ “ Aug. 19, 1893 

“ “ “ 7 times during 1869-1891 

tt ii if ^ ft ft( it it 

tt ti it ^ it ti «t tt 

“ “ “ May 4, 1893 

“ “ “ 1882 [sewer) 

“ “ “ July 6, 1896. (Gorged a 

Brooklyn, N. Y. 

Spring Mount, Pa., June 6, 1893 

“ “ “ during 1893 (4 storms) 

Philadelphia, Pa., 2 times during 1884-1891 

it ii ^ tt it it it 

tt it ^ % t tt tt tt 

“ “ March, 1890 

Baltimore, 1896 


Washington, D. C., 2 times during 1871-1891 


tt 

tt 

>0 0 

M 

it 

ii 

it 

ii 

tt 

tt 

ii 

11 

it 

ii 

ii 

ii 


“ “ mean of many rains 

New Orleans, June 17, 1895 
Aug. 13, 1894 

“ July 4, “ 

“ “ “ X4, “ 

“ “ Sept., 1889 (2 storms) 

“ April 24, 1894. Preceded by 

6 hours of light rain 

(Jacksonville, Fla., U. S. Weather Bureau, 
^ 1896 

[Galveston, Texas, 1896. U. S. Weather 
j Bureau 

Chicago, once during 1889-1891 
“ 2 times “ “ “ 

tt ^ tt ti tt it 

Ohio Valley, July 16, 1896 
St. Louis, May 14, 1891 
Cleveland, Ohio, 1896 

tt tt ti 


Detroit, Mich., “ I U. S. Weather 
“ “ “ r Bureau 

Little Rock, Ark., “ 

i* tt t't tt 

San Diego, Cal., December, 1896 
Campo, Cal., August, 1891 
Palmetto, Nev., “ 1890 

j- Island of St. Kitts 

























































































































AMOUNT OF SEWAGE. 


47 


Art. 18. Run-off Data. 

The data concerning rates of run-off as compared with 
rainfall during the same time are very meagre. The total 
annual or monthly proportion of run-off has been ascertained 
in many different localities, but even this is for natural 
wooded surfaces or fields only. The number of careful gaug- 
ings in this country of rainfall within city limits and of con¬ 
temporaneous sewer discharge from a known area probably 
does not exceed a half dozen. 

One of the most recent, extensive, and scientific of such 
gaugings was that made at New Orleans in 1894-5 under the 
direction of the Engineering Committee on Drainage. Un¬ 
fortunately for its general usefulness in the study of run-off 
problems the run-off measured probably included seepage 
from a soil lower than, and consequently more or less saturated 
by, the Mississippi River. The rainfall was recorded contin¬ 
uously at several points throughout the city, and several of 
the maximum rates are given in Table No. 9. A continuous 
record was also kept of the amount of water reaching the 
drainage-ditches from above and beneath the surface of the 
soil. From data thus and otherwise obtained the committee 
prepared curve-diagrams (Plate No. II) for the calculation of 
run-off from areas of different extent, character, and grade of 
surface in New Orleans. “ The set marked A represents the 
run-off from densely built-up parts; the set marked B applies 
to the areas having small yards, or a medium density of 
population; the set marked C applies to the sparsely built-up 
parts, or those having large yards; and the set marked D 
applies to the rural areas. These curves, therefore, indicate 
the maximum rate of rainfall which it is proposed to provide 
for, and which is assumed to reach the drains and canals from 
the respective areas. 

“ They do not warrant the assumption, however, that the 


48 


SEWERAGE . 


discharge will never exceed the quantities given for it; in fact 
it is certain that they will be exceeded, but at such rare and 
indefinite intervals that their consideration is not justified. It 
should also be remarked that the curves are based upon the 
assumption that . . . the water enters the drains promptly, 
as is the case in most other cities.” (Report of the Engineer¬ 
ing Committee—B. M. Harrod, Henry B. Richardson, and 
Rudolph Hering—on the Drainage of the City of New 
Orleans; 1895.) 

A number of gaugings have been made in Washington, 
D. C., in districts whose streets are almost entirely paved 
with asphalt. In one case “ the flow in the sewer rose 
almost immediately after the rain began and fell to its normal 
level within a few minutes after the rain ceased.” During 
another storm “ at its maximum period the rain fell for 37 
minutes at the rate of 0.9 of an inch per hour. The sewer- 
gauge rose to a height of 3.7 feet, giving about 0.47 of the 
capacity of the sewer and indicating no loss whatever by 
absorption or evaporation during the time of maximum flow. ’ * 
(Hoxie on “ Excessive Rainfalls,” Transactions Am. Soc. 
C. E., vol. XXV.) This sewer received the drainage of 200 
acres. 

Gaugings made in Rochester by Emil Kuichling are too 
extensive to be quoted here, but the tables may be found in 
the Transactions Am. Soc. C. E., vol. XX, pages 1-60, 
accompanied by an excellent discussion on the subject of run¬ 
off. The conclusions drawn from these by the author of that 
paper are quoted, as stating clearly the general principles on 
which are founded the rational methods of calculating run-off. 
The gaugings, he says, “ point unmistakably to the following 
general conclusions: 

“ 1. The percentage of the rainfall discharged from any 
given drainage-area is nearly constant for rains of all consider¬ 
able intensity and lasting equal periods of time. This cir- 


AREA DRAINED IN ACRES AREA DRAINED IN ACRES 


AMOUNT OF SEWAGE, 


49 


Plate II. 

MAXIMUM FLOW FROM DRAINAGE AREA IN CUBIC FEET PER SECOND 

































































































































































































































































































































































































































































































































































































































































































































































50 


SE WEE A GE. 


cumstance can be attributed only to the fact that the amount 
of impervious surface on a definite drainage-area is also 
practically constant during the time occupied by the experi¬ 
ments. 

“2. The said percentage varies directly with the degree 
of urban development of the district, or, in other words, with 
the amount of impervious surface thereon. . . . 

“3. The said percentage increases rapidly, and directly 
or uniformly with the duration of the maximum intensity of 
the rainfall, until a period is reached which is equal to the 
time required for the concentration of the drainage-waters 
from the entire tributary area at the point of observation; 
but if the rainfall continues at the same intensity for a long 
period, the said percentage will continue to increase for the 
additional interval of time at a much smaller rate than pre¬ 
viously. This circumstance is manifestly attributable to the 
fact that the permeable surface is gradually becoming satu¬ 
rated and is beginning to shed some of the water falling upon 
it; or, in other words, the proportion of impervious surface 
slowly increases with the duration of the rainfall. 

“ 4. The said percentage becomes larger when a moderate 
rain has immediately preceded a heavy shower, thereby par¬ 
tially saturating the permeable territory and correspondingly 
increasing the extent of impervious surface. 

“5. The sewer discharge varies promptly with all appre¬ 
ciable fluctuations in the intensity of the rainfall and thus 
constitutes an exceedingly sensitive index of the rain and its 
variations of intensity. 

** 6. The diagrams also show that the time when the rate 
of increase in the said percentage of discharge changes 
abruptly from a high to a low figure agrees closely with the 
computed lengths of time required for the concentration of the 
storm-waters from the whole tributary area, and hence the 
said percentages at such times may be taken as the proportion 





AMOUNT OF SEWAGE. 


51 


of impervious surface upon the respective areas.” (Transac¬ 
tions Am. Soc. C. E., vol. XX, page 37.) 

“ The Nagpoor (India) storage reservoir receives the 
flow from a watershed of 6.6 square miles. With a very 
absorbent natural surface that watershed has nevertheless 
delivered to the reservoir in 170 minutes 98$ of a downpour 
upon its entire area of 2.2 inches in 80 minutes, when the 
power of absorption of the soil had been satisfied.” (Hoxie). 

Many instances could be named where storm-sewers which 
were designed to carry a run-off of one cubic foot per second 
have caused serious damage by their too small capacity; 
several where even a capacity of two cubic feet per second 
was insufficient. (One inch of rainfall per hour equals one 
cubic foot per second per acre almost exactly.) Not many 
years ago a sewer was considered by most engineers to be of 
ample size if it was designed for a rainfall of one inch per 
hour, one half running off; but the insufficiency of this rule 
has been learned by costly experience. 

Accounts of accidents through insufficient sewer dimen¬ 
sions are unfortunately more numerous than data giving exact 
figures of unusual volumes of rainfall reaching sewers. 

An analysis of the available data seems to point to the 
following conclusions: 

That the total run-off from any area is directly propor¬ 
tional to the imperviousness of the surface, and that this 
imperviousness increases with the length of the storm, unless 
it is already 100$. 

That very nearly 100$ of the water falling upon an im¬ 
pervious surface flows immediately to the sewer unless held 
back by obstructions in the street, roof-gutters, or sewer- 
inlets—the last including insufficiency of size of the inlet. A 
small percentage, however, is usually evaporated at once. 

That the proportion of the rainfall on any given imper¬ 
vious area which reaches any particular point in the sewer 


52 


SE WE ft A GE. 


system increases with the length of the storm up to the 
time when the run-off from the most distant part of said area 
reaches the point of observation; after which the run-off very 
nearly equals the rainfall upon said area while the rate of fall 
remains constant. 

That the percentage of imperviousness of the surface may 
vary from o % to 100$, being the first in the case of very 
porous soil under natural conditions at the beginning of a rain, 
and the last in an urban district where streets, sidewalks, and 
yards are all paved, or occasionally where a dense clay soil is 
saturated by previous rainfall. 


Art. 19. Formulas for Storm-water Run-off. 


Many attempts have been made to construct a simple 
general formula for obtaining the run-off from any area. The 
best known of these are as follows: 


Craig: 


Dredge: 


Dickens: 


Fanning: 


D — ^oBN hyp. log 

D — discharge in cubic feet per second; 

L — extreme length of drainage-area; 

B — mean breadth of drainage-area; 

N — constant varying from 0.37 to 1.95. 

^ M 

Q = 1 30o^j. 

L — length of watershed; 

M — area in square miles. 

D = 825 MK 

D — discharge in cubic feet per second; 
M = drainage-area in square miles. 

Q = 200 MK 

Q = discharge in cubic feet per second; 
M — drainage-area in square miles. 



AMOUNT OF SEWAGE, 


53 


Burkli-Ziegler: Q = Rc^f 


Kirkwood: 


Hawksley: log D = 


c — constant—0.75 for paved streets, 0.31 for 
macadamized streets; 

R — average rate during heaviest fall in cubic 
feet per second per acre; 

5 = general fall of area per 1000; 

Q = cubic feet per second per acre reaching 

sewers; 

A — drainage-area in acres. 

N' y 

I5804 SJ * 

D = diameter of sewer in feet* 

.S' = sine of inclination; 

N — number of acres in area. 

Maximum rainfall of one inch, one half running off. 

3 log A + log N -f 6.8 


D 


= (- 


10 


Adams: log D 


D = diameter of sewer in inches; 

A = number of acres to be drained; 

N — length in feet in which sewer falls one 
foot. 

City or suburban surfaces. 

2 log A + log -A — 3-79 


A = area in acres; 

TV' — as in Hawksley; 

D — diameter in feet. 

For one inch rainfall, one half running off. 


McMath: 


Q = Rc 



s_ 

A * 

Terms as in Burkli-Ziegler; R taken at St. 
Louis as 2.75 inches. 


I 






54 

Kuichling: 


SJB WEE A GE. 


Q = Aat(b — ct). 

Q = discharge in cubic feet per second; 

A = drainage-area in acres; 
t = duration in minutes of the intensity 
(b — ct) ; 

£ = 2.i \ for Rochester, N. Y. (Kuich- 

c — 0.0205 ) ling recently gives as a for¬ 
mula representing storms of 
the second class at Rochester: 

r = —7, in which r = rate in 
t ‘° 6 

inches per hour.) 
proportion of impervious surface 


The following, known as Roe’s tables, gives the number 
of acres of urban surfaces which can be drained by sewers of 
different diameters and at different grades. It is no longer 
in general use. 


Inclination, Fall, or Slope 
of Sewer. 


Level. 


£ in. in 

10 ft., 

or 

1: 480. 

i “ “ 

4 4 4 4 

4 4 

1:240. 

t “ “ 

4 4 4 4 

4 4 

1: 160. 

j 4 i 44 

4 4 4 4 

4 4 

1: 120. 

i£“ “ 

4 4 4 4 

4 4 

1: 80.. 

2 “ “ 

4 4 4 4 

44 

1:60.. 


Inner Diameter or 


2 

2i 

3 

4 

5 

39 

67 

120 

277 

570 

43 

75 

135 

30S 

630 

50 

87 

155 

355 

735 

63 

113 

203 

460 

950 

78 

M3 

257 

590 

1200 

90 

165 

295 

670 

1385 

115 

182 

318 

730 

1500 


Bore of Sewer in Feet. 


6 

7 

8 

9 

IO 

1020 

1725 

2850 

4125 

5825 

III7 

1925 

3025 

442 5 

6250 

1318 

2225 

3500 

5100 

7175 

1692 

2375 

4500 

6575 

925O 

2180 

3700 

5825 

7850 

11,050 

2486 

422S 

662 



2675 

4550 

7125 




The formulas of Craig, Dredge, Dickens, and Fanning 
apply to natural surfaces and have the shape and extent of 
the drainage-area as the only variables. The Biirkli-Ziegler, 
Kirkwood, and McMath formulas take into account also the 
slope of the surface. The Biirkli-Ziegler and Kuichling allow 
for varying conditions of surface, and, together with the 
McMath, for varying rates of rainfall. All these formulas 
except the three last mentioned are based on an assumed 
maximum rate of rainfall. 








































AMOUNT OF SEWAGE. 


55 


Roe’s tables give the diameter of sewer necessary to meet 
various conditions of area and sewer grade. As in a level 
sewer the surface of the water must have some fall if there is 
to be any flow, the quantities given for a level grade can 
apply only to a limited length of sewer. None of these 
formulas is satisfactory for all cases, because none takes into 
account all the variable conditions. Those which are prob¬ 
ably the most frequently used are the Bilrkli-Ziegler, 
McMath, and Kuichling, and these are seen to be the ones 
containing the most variables. The proper test of any 
formula is to calculate by it from known data quantities 
which are also known. Many such tests of all these formulas 
have been made, and it has been found that there are few, if 
any, cases in which all will give results practically identical or 
equal to the actual quantities as measured. Such a compari¬ 
son is given of Roe’s tables, Hawksley’s, Kirkwood’s, and 
Biirkli-Ziegler’s formulas, and the actual gaugings of a sewer 
in Washington made in 1884 (from paper by Capt. R. L. 
Hoxie read before the Am. Soc. C. E. July 2, 1886): 


Rainfall. 

Roe’s Tables. 

Hawksley. 

Kirkwood. 

Biirkli- 

Ziegler. 

Actual 

Maximum 

Flow. 

0.5" in 1 5 min... . 

36.3 

43-2 

5 i -7 

137-6 

300 

0.55" in 37 min.. 

36 3 

43-2 

51.7 

61. g 

180 


The discrepancies are largely due to the causes already 
referred to—that factors are taken as constants which are 
really variables, and hence each formula can give correct 
results for certain cases only. In most the constant is sup¬ 
posed to be derived from maximum rates of rainfall, but such 
data were until recently incomplete and inaccurate. Also, 
since the authors of the older formulas were Europeans or 
derived their data from European sources, the maximums 
were those for Europe and are not applicable to this country. 
Also the character of the majority of city-street surfaces has 


















56 


SEWERAGE. 


changed since that time. The Kuichling, Biirkli-Ziegler, and 

McMath formulas recognize the variableness in drainage- 

$ 

surfaces. 

It is possible that a formula can be devised which shall 
represent by variable factors all the conditions which have 
been shown to affect the run-off. But it can hardly be 
expected that such a formula can be other than cumbersome; 
and it is probable that the shortest method which is at all 
rational and accurate in all cases is that of subdividing the 
calculation, and adapting a general method rather than a 
general formula to the peculiar conditions of each case. 
Such a method is recommended and will be outlined further 
on. 

Many engineers, however, use some one of the formulas 
given, and a large majority of the storm-sewers built in this 
country are probably so designed—in spite of the fact that 
McMath considers his formula (which is probably the most 
popular) as adapted to large areas only, and that it is derived 
in an entirely empirical manner from St. Louis data only; and 
that Kuichling has “ finally abandoned the attempt to estab¬ 
lish a general formula for run-off,” although the one bearing 
his name is largely general in application and rational in origin 
and construction. 

Art. 20. Expediency of Providing for Excessive 

Storms. 

An examination of rainfall records shows no apparent law 
of frequency of excessive storms. It can be said as a general 
statement, however, that a rate of fall within certain limits 
may be expected almost any month; one within higher limits 
five or more times in ten years (these are the storms referred 
to in Art. 17); and a phenomenal downpour at most irregular 
intervals, usually many years apart. Should the sewer be 
designed to carry the run-off from storms of the first class 


AMOUNT OF SEWAGE. 57 

only, of the second class, or be of the greatest size demanded 

bv the third class ? 

* 

That the last is desirable will not be disputed, but both 
practical and financial difficulties frequently oppose this 
course. The practical ones, however, in most, if not all, cases 
resolve themselves into financial ones; and the question 
becomes one of dollars and cents, and to a certain extent also 
of public convenience, which cannot be assigned a money 
value. To accommodate the second class of storms may 
require a sewer of three or four times the capacity of one 
which would suffice for the run-off from the first class, and 
the third class a capacity two or three times that of the 
second. The result of providing capacity for the first class 
only would probably be flooding of streets and cellars one or 
more times almost every year; for the second class, flooding 
at intervals of several years; for the third class, perfect 
immunity from floods. 

The loss resulting from a flooding of streets and cellars by 
water more or less foul may be very considerable; goods may 
be damaged, business suspended, foundations weakened, 
health threatened by the dampness lingering after the floods 
have withdrawn; also real-estate values in a district liable to 
floods will depreciate and the city as a whole will be a loser 
by increased tax rates to meet the decreased valuation. On 
the other hand as the capacity of a sewer increases so does 
the cost, and this fact may place an urgent, even an impera¬ 
tive, limit to either the capacity or the extent of the sewers to 
be built. The relative cost of sewers of different capacities 
(other things supposedly equal) in Washington, D. C., for 
about io years is given in the following table (adapted from 
one prepared by Capt. Hoxie). The unit of capacity is that 
of a 12-inch pipe. 

The exact proportion between the capacity and the cost, 
and the rule of their relative increase, will vary with different. 


/ 



SEWERAGE. 
Table No. 10. 


Number of 
Units of 
Capacity. 

Relative 

Cost 

per Foot. 

Number of 
Units of 
Capacity. 

Relative 

Cost 

per Foot. 

Number of 
Units of 
Capacity. 

Relative 

Cost 

per Foot. 

I 

I OOO 

6 

I.920 

20 

3.170 

2 

1.174 

7 

2.090 

30 

3.480 

3 

1.388 

8 

2.250 

40 

4.030 

4 

I -567 

9 

2.410 

50 

4.170 

5 

1.743 

10 

2.570 




methods of construction, depth of sewer, etc.; and in many 
localities the cost will be found to increase more rapidly 
relative to the capacity than is indicated by Table No. io. 
But in any case it will be found that the increase of cost is 
much less rapid than that of capacity. Using the table of 
cost of Washington sewers, a sewer of three times the capacity 
of a 12-inch pipe would cost 1.388 units of value. If this 
would just suffice for the heaviest storms of the first class on 
a given area one of a capacity ample for the maximum of the 
second class, or four times as great, would cost 2.8 units of 
value, or about twice as much; and one capable of removing 
the run-off from the greatest downpours, or twelve times 
capacity of the first, would cost 3.75 units of value, or only 
2.7 times as much as the first. Moreover, as we shall see 
later, the larger mains need to increase less rapidly in capacity, 
and hence in cost, to accommodate the heavier storms than 
do the smaller laterals used in this illustration. 

The decision as to which class of storms the size shall be 
adapted to must be made for each case by the engineer or 
the city authorities as their judgment dictates. But prob¬ 
ably in nine cases out of ten the truest economy will be 
observed by constructing sewers sufficient for the second, or 
even in some cases the third, class of storms. The damage 
likely to result from the use of sewers of too small capacity, 
which damage is to be balanced against the extra cost of 
larger ones, will depend upon circumstances. “ If the sur- 
















A MO UNT OF SEWAGE . 


59 


face flow upon the streets passes off to a proper outlet with¬ 
out causing damage or inconvenience the flood is well 
disposed of. If not, there is danger in permitting storm¬ 
water to accumulate upon streets with steep grades. It 
becomes a torrent flowing with great velocity, and cannot 
then be captured by inlets designed to arrest, each, its share 
of shallow gutter flow with small velocity. It moves rapidly 
down to valleys or basins without surface outlet; here it 
floods the surface, because inlets to receive it as fast as it 
comes can rarely be constructed—even should the drains here 
be of sufficient capacity. Inlets for large volumes of water 
in city streets are apt to be pitfalls for pedestrians and traps 
for cart-wheels and horses’ feet. If the drains of the inun¬ 
dated district are of insufficient capacity the consquences are, 
of course, disastrous.” (Hoxie, “ Excessive Rainfalls.”) 

As suggested in this quotation, it is possible in many 
localities to lead the surplus water of severe storms over the 
surface to the nearest natural watercourse, and this without 
any damage resulting, although it may be temporarily incon¬ 
venient. But in a city where all small streams have been 
walled in or diverted to sewers this is possible only along a 
water front. 


CHAPTER IV. 


FLOW IN SEWERS. 

Art. 21. Fundamental Theories. 

The flow in an ordinary sewer must be due to one cause 
only—the attraction of gravitation. The velocity of this flow 
is retarded by friction and other obstacles affecting it along 
the line of the sewer. 

The general formula for the velocity due to gravity of a 
freely falling body is V— V 2 gh } where V is velocity in feet 
per second, h is head in feet, and g is acceleration due to 
gravity, being about 32.16 feet per second. In the case of 
running water h is the fall of the surface of the water from 
the point of no motion to the point in question. Therefore 
if there were no opposing forces a stream would flow more 
and more rapidly along its course as the total head became 
greater; and its velocity would become constant only when 
the surface was level, and therefore h constant. There is, 
however, friction between the moving water and the sides of 
a sewer, and this must be overcome by some force. Since 
the only force available is that due to gravity, called into play 
by the creation of a head /z, a part of this force must be used 
in overcoming friction. If it is not all so used the remainder 
goes to create additional velocity. Friction, it is found, 
increases with the velocity of the moving body, so that, as 
additional increments of speed are created by /z, a larger pro¬ 
portion of the head is consumed in overcoming friction, until 
at last all of h is so consumed and none goes to increasing the 

60 



FLOW IN SEWERS. 


61 


velocity—that is, the velocity remains constant. Friction also 
varies with the roughness of the surface. The total amount 
of energy lost in friction also increases with the duration of its 
action, which is proportional to the distance travelled /. It 
is found that at least one other condition affects the amount 
of friction in sewers, viz., the proportion between the cross- 
sectional area of the stream and the length in this cross-section 
of the line of contact between the water and the bed of the 
stream; the greater the first is in proportion to the second the 
less the effect of friction upon the mass as a whole. This 

area of section 

proportion, or ---:--—, is customarily represented 

1 1 wetted perimeter 

by R and is called “ hydraulic radius ” or mean depth.” 

From these considerations it follows that V varies as V 2 gh 
and as f(R), and inversely as f(l). The effect of roughness 
may be represented by a factor a » A formula for velocity 


In 1753 


\Z 2 gZif (R\ 

would therefore be in the form V = a -——--. 

J\r) 

Brahms proposed as a formula representing the resultant effect 
of these accelerating and retarding influences V = c VRS , in 
which V = mean velocity of current, c is an empirical constant 
which includes V^and a , R is the hydraulic radius, and S is 

h 

the sine of the surface slope, or j. This formula, now gen¬ 


erally called Chdzy’s formula, has been made the basis of 
others, most of which differ among themselves only in the 
values given to c\ but it is now recognized that V does 
not vary exactly as the square root of R and of 5 ; that is, 

\Z 2ghf 

that f(R) and /(/) in the formula V = a -—- are not 

exactly VR and Vl\ but they approximate it, and this 
formula may therefore be written 















62 


SE WE A A GE. 



From this 


it follows that c is not a constant for any particular sewer or 
stream, but varies with both R and 5 . The principal cause 
affecting the value of c> however, is the condition as to 
roughness of the wetted perimeter. 


If we wish to obtain the velocity of flow in any sewer by 


this formula it is necessary to select proper values for c, R, 
and 5 . 5 can be readily obtained by dividing h by /. The 

value of c and R and their relation to V will now be discussed. 

For c most of the older formulas give constant values; but 
since V varies with different materials of channel-walls, whose 
character does not affect the values of R and 5 , this variation 
must be recognized in a variable c by means of a new factor 
or by a new equation. Most of the efforts looking to greater 
accuracy have been directed toward determining values for 
c and thousands of experiments have been made for this 
purpose. D’Arcy’s value, somewhat simplified and for feet 
measure, is 



Bazin’s value for cut stone and brick-work is 



Eytelwein’s value is c = 93.4. 

The formula evolved from the records of a large number 
of experiments by Messrs. Ganguillet and Kutter, usually 
called “ Kutter’s formula,” is now generally held to give 
results more nearly approximating the actual velocities than 
any other. This formula is, for English measure, 


4 i. 6 -\ j b 


00281 . 1.811 











FLOW IN SEWERS. 


63 


in which n is a “ coefficient of roughness ” of the sides of the 
channel, such coefficient having been obtained by averaging 
many experiments. In the selection of value for n great care 
and judgment must be exercised, particularly for small 
sewers, in the calculation for which n has a greater effect than 
in that for large channels. 

The values of 71 are approximately: 

Sides and bottom of channel lined with well-planed timber. .009 
With neat cement, clean glazed sewer-pipe, and very 


smooth iron pipe.010 

With 1 -.3 cement mortar or smooth iron pipe.oil 

With unplaned timber and ordinary iron pipe.012 

With smooth brick-work or ordinary pipe sewers.013 

With ordinary brick-work .015 

With rubble or granite-block paving.017 


Kutter’s formula is seen to provide for variations in c due 
not only to the character of the channel but also to changes 
in R and 5 . 

This formula has been used to calculate the tables Nos. 
11 and 12, n being taken as .013 in the former and .015 in 
the latter. If it is desired to use another value of n the 
corresponding values of velocity and discharge can be obtained 
very approximately by multiplying the quantities given in 
each table by the factors given below it for that purpose. 
For ordinary pipe or good brick sewers 7 i may be taken as 
.013, for ordinary brick or smooth stone as .015. For extra 
smooth work n may be taken as .011. 

The uncertainties necessarily existing in the estimates of 
the amount of sewage to be provided for and the difficulty of 
selecting just the proper value for n , owing to the non- 
uniform character of the interior surface of the sewer, make a 
refinement of calculations out of keeping with the data used. 
Moreover, in the case of vitrified clay or concrete pipe the 








64 


SEWEXAGE, 


Table No. 11 . 

VELOCITY AND DISCHARGE IN SEWERS 4 TO 36 INCHES DIAMETER. 

Velocity in Feet per Second; Discharge in Cubic Feet per Minute; Sewers Flowing 

Full. 


(Formula V = c RS\ c calculated by Rutter's formula, with n = .013. Q = 60 aV.) 


v*-s 

5 u 

4 / V 

4-inch 

6-inch 

8-inch 

10-inch 

12-inch 

15- 

inch 

18-inch 


V 

Q 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

.1 

5-75 

30-13 

7-99 

94.10 

IO.O4 

210.3 

II.94 

39°-8 

13.73 

647.0 

16.24 

1196.0 

18.59 

i 97 i -5 

°5 

4.06 

21.28 

5.64 

66.48 

7.O9 

148.6 

8-43 

276.1 

9.70 

457-1 

11.48 

8450 

13.13 

i 393 -o 

.04 

3-63 

19 03 

5 05 

59 45 

6.34 

132.9 

7-54 

246.9 

8.65 

407.8 

10.26 

755-6 

11.74 

1244.0 

.03 

3-15 

16.47 

4-25 

50.01 

5-49 

115-0 

6-53 

213.7 

7.51 

353-9 

8.89 

654-4 

10.17 

1078.0 

02 

2-57 

13-44 

3-56 

42.00 

4.48 

93-90 

5-33 

174.5 

6.13 

289.0 

7.25 

534-2 

8.30 

880.4 

.01 

1.82 

9-50 

2.52 

29.70 

3 -i 7 

66.3S 

3-77 

123.4 

4-33 

204.3 

5.13 

377-8 

587 

622.6 

.008 

1.61 

8-37 

2.25 

26.53 

2.83 

59-35 

3-37 

110.3 

3-87 

182.6 

4.59 

337-7 

5.25 

556.8 

.006 

1.38 

7 18 

i -95 

23.00 

2-45 

51-39 

2.92 

95-55 

3-35 

158.2 

3.97 

292.5 

4-55 

482.3 

.004 



1.59 

18.71 

2.00 

41.85 

2.38 

77.98 

2-74 

129.1 

3.24 

238.3 

3-70 

392.9 

.002 





1.40 

29.38 

1.67 

54 - 6 i 

1.91 

90.40 

2.27 

167.3 

2.60 

275-9 

.001 







1 .17 

38.41 

1-35 

63-58 

1.60 

II 7-7 

1.83 

194-3 

0009 











1.51 

hi.4 

1.73 

183.9 

0008 













1.63 

I 73 -I 

0007 













1.52 

161.2 


For« = .on .012 .013 .015 .017 

Multiply V or Q by 1.20 1.09 1.00 0.84 0.73 


I gallon per day =~ .00009284 cubic feet per minute. 
I. cubic foot per minute — 10,771 gallons per day. 

























































FLOW IN SEWERS. 


65 


Table No. 11. — Continued. 

VELOCITY AND DISCHARGE IN SEWERS 4 TO 36 INCHES DIAMETER. 

Velocity in Feet per Second ; Discharge in Cubic Feet per Minute , Sewers 

Flowing Full. 

(Formula V = c V RS ; c calculated by Kutter’s formula, with n — .013. Q = 6 oaV.) 


Grade of 
Sewer. 

20-inch 

22-inch 

24-inch 

30-inch 

33-inch 

36-inch 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

.1 

20.08 

2628 

21.51 

3407 

22.91 

4319 

26.84 

7905 

28.69 

10220 

30.46 

12920 

.05 

14.18 

1857 

15.20 

2407 

16.19 

3052 

18.97 

5586 

20.27 

7225 

21.54 

9136 

.04 

12.69 

1661 

13-59 

2153 

14.47 

2729 

16.96 

4995 

13.13 

6461 

19.26 

8171 

-03 

IO.98 

1438 

11.77 

1864 

12.53 

2363 

14.69 

4325 

15-70 

5595 

16.68 

7075 

„02 

8.97 

1174 

9.61 

1522 

IO.23 

1930 

n -99 

3532 

12.82 

4568 

13.62 

5777 

.OI 

6-34 

830 

6.79 

1076 

7.24 

1396 

8.48 

2497 

9.06 

3230 

9-63 

4085 

.008 

5-67 

742 

6.07 

962 

6.47 

1220 

7.58 

2233 

8.11 

2889 

8.61 

3653 

.006 

4.9 1 

643 

5-26 

833 

5.60 

1057 

6.57 

1934 

7.02 

2502 

7.46 

3164 

.004 

4.OO 

524 

4.29 

679 

4-56 

860 

5-35 

1576 

5-72 

2040 

6.08 

2580 

.002 

2.8l 

368 

3.01 

477 

3.21 

605 

3-76 

1109 

4.02 

1434 

4.28 

1814 

OOI 

I.98 

259 

2.12 

336 

2.26 

427 

2.66 

782 

2.84 

1012 

3.02 

1281 

.OOO9 

I .87 

245 

2.01 

3 j 8 

2.14 

404 

2.51 

74 i 

2.69 

959 

2.86 

1213 

.0008 

I.76 

231 

1 .89 

299 

2.02 

3 So 

2-37 

697 

2-53 

902 

2.69 

1141 

.0007 

I.64 

215 

1.76 

279 

1.88 

354 

2.20 

650 

2.36 

841 

2.51 

1065 

.0006 

I. 51 

198 

1.63 

258 

i -73 

327 

2.04 

600 

2.18 

777 

2.32 

984 

.0005 



1.48 

234 

1.58 

298 

1.86 

546 

1.99 

708 

2.11 

896 

.0004 



1.32 

208 

1.40 

265 

1.65 

486 

i -77 

630 

1.88 

798 

.0003 





1.20 

227 

1.40 

413 

1-52 

54 i 

1.62 

686 

.0002 





0.96 

186 

r-i 3 

335 

1.22 

435 

1.3c 

552 





















































66 


SEWERAGE , 


Table No. 12 . 

VELOCITY AND DISCHARGE IN SEWERS 33 INCHES TO IO FEET 

DIAMETER. 


Velocity in Feet per Second; Discharge in Cubic Feet per Minute; Sewers 

Flowing Full. 

(Formula V — c V RS ; c calculated by Kutter’s formula, with n = .015. Q = 60 aV.) 


Grade of 

33 

-inch 

36-inch 

42 

-inch 

4 

■foot 

Sewer. 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

•05 

17.17 

6120 

18.27 

7750 

20.37 

11765 

22.36 

16865 

.04 

15.36 

5473 

16.34 

6930 

18.21 

10517 

20.00 

15080 

•03 

13-30 

4738 

14.15 

6000 

15-77 

9108 

13.31 

13057 

.02 

IO.85 

3868 

11.55 

4900 

12.88 

7437 

I 4 .I 3 

10658 

.01 

7.68 

2735 

8.16 

3464 

8.90 

5258 

9.99 

7537 

.008 

6.86 

2444 

7.30 

3096 

rj- 

CO 

4700 

8-93 

6738 

.OO6 

5-94 

2115 

6.32 

2679 

7.04 

4067 

7-73 

5832 

.004 

4.84 

1726 

5-15 

2186 

5 - 75 

3243 

6.31 

4759 

.002 

3 - 4 i 

1216 

3.63 

1540 

4-05 

2339 

4-45 

3354 

.001 

2.40 

856 

2.52 

1085 

2.85 

1648 

3-13 

2365 

.0009 

2.27 

810 

2.42 

1027 

2.70 

1561 

2.97 

224O' 

.0008 

2.14 

763 

2.28 

967 

2-55 

1470 

2.80 

2110 

.0007 

2.00 

713 

2.13 

903 

2.38 

1373 

2.61 

1972: 

.0006 

1.85 

658 

1.97 

834 

2.20 

1269 

2.42 

1822 

.0005 

1.68 

598 

1.79 

759 

i -95 

1128 

2.20 

1658 

.0004 

1.49 

532 

1-59 

675 

1.78 

1028 

1.96 

1477 

.0003 

1.28 

457 

1-37 

580 

1.53 

883 

1.68 

1270 

.0002 

.00015 





1.23 

712 

1.36 

1.16 

102b 

878 


For n= .011 .012 .013 .015 .017 

Multiply V or Q by 1.43 1.29 1.19 1.00 0.87 




























FLOW IN SEWERS. 


6/ 


Table No 12 .— Continued. 

VELOCITY AND DISCHARGE IN SEWERS 33 INCHES TO IO FEET 

DIAMETER. 


Velocity in Feet per Second; Discharge in Cubic Feet per Minute; Sewers 

Flowing Full. 

(Formula F = c y RS ; c calculated by Kutter’s formula, with n = .015. Q — 60 aV.) 


Grade of 

5 - 

foot 

6-foot 

8-foot 

IO 

-foot 

Sewer. 

V 

Q 

V 

Q 

V 

Q 

V 

Q 

.05 

26.05 

30700 







.04 

23.30 

27450 

26.34 

44690 





•03 

20.17 

23765 

22.8l 

38700 





.02 

16.47 

19405 

18.62 

31600 

22.53 

67965 

26.03 

122700 

.01 

11.64 

13717 

13-17 

22345 

15-93 

48050 

18.41 

86755 

• 008 

10.41 

12267 

II.78 

19980 

14.25 

42970 

16.46 

77590 

.006 

9.01 

10617 

IO.19 

17295 

12.33 

37200 

14.25 

67175 

.004 

7-36 

8665 

8.32 

14113 

10.07 

30370 

11.63 

54840 

.002 

5-19 

6110 

5-87 

9956 

7.10 

21435 

8.21 

38720 

• OOI 

3-66 

4311 

4.14 

7030 

5.02 

15150 

5.81 

27380 

.OOO9 

3*47 

4083 

3-92 

6659 

4.76 

14353 

5 - 5 i 

25960 

.0008 

3-27 

3849 

3-70 

6276 

4.49 

13533 

5-19 

24475 

.0007 

3-05 

3597 

3-46 

5870 

4.20 

12660 

4.86 

22895 

.0006 

2.82 

3326 

3.20 

5429 

3-88 

11710 

4-50 

21195 

.0005 

2-57 

3028 

2.92 

4946 

3-54 

10675 

4.10 

19325 

.0004 

2.29 

2700 

2.60 

4411 

3.16 

9532 

3-66 

17267 

.0003 

1.97 

2324 

2.24 

3801 

2.73 

8228 

3 -i 7 

14927 

.0002 

1.60 

1882 

1.82 

3083 

2.22 

6694 

2.58 

12168 

.00015 

1.37 

1615 

1.56 

2650 

1-93 

5820 

2.23 

10510 

.00012 



i -39 

2353 

1.70 

5137 

1.99 

9375 

.OOOIO 





i -55 

4672 

1.81 

8542 

.000095 





1.25 

3783 

i -77 

8320 

.OOOO9O 




' 



1.72 

8096 


































68 


SE WEE A GE. 


market sizes must in the end be those selected, and there is 
a considerable jump between the capacities of consecutive 
sizes. For instance, an 8-inch pipe on a grade will dis¬ 
charge about 498 gallons per minute when running full; a 
10-inch pipe running full with the same grade will discharge 
about 925 gallons per minute, and a 12-inch pipe about 1530 
gallons per minute. For this reason it is sufficiently accurate 
and often more convenient to use curves plotted from the 
tables, having the grade and corresponding velocity or dis¬ 
charge as coordinates, from which the flow through any cus¬ 
tomary size of sewer at any practicable grade can be found at 
a glance and with as great accuracy as is required for ordinary 
use. Such a diagram can be readily prepared on a sheet of 
cross-section paper, a curve being drawn for the velocity and 
another for the discharge of each size of sewer. 

It is now generally considered that Kutter’s formula gives 
somewhat too small values for sewers under 15 or 18 inches 
diameter. 

It must be remembered that the formulas and tables of 
velocity are supposed to apply only when the sewage has 
reached a constant velocity. Previous to this when the fric¬ 
tion does not consume all of h the remainder is creating 
increments of velocity. Since the same amount of sewage 
must pass all sections of a sewer between two inlets, however, 
it follows that, previous to the flow obtaining its maximum 
and constant velocity, the depth of sewage must have been 
greater, increasing up stream to the point of entry. An 
initial velocity of entrance in the direction of the sewage flow 
will reduce the amount and extent of this non-uniform flow 
with larger cross-section, but will have little effect upon the 
ultimate constant velocity. If no such initial velocity exist 
the entering sewage must, if it be any large percentage of the 
capacity of the sewer, back up the feeding-pipe through which 
it entered in order to create additional head h. 





FLOW IN SEWERS . 


69 


V is the mean velocity. The effect of friction is exerted 

along the wetted perimeter and grows less toward the centre 

of the stream. The surface of flow is also retarded by friction 

with the air, and frequently in the case of house-sewage by 

a greasy scum which floats upon the surface. The velocity 

given is really the volume of flow divided by its area. 

( area \ 

——---j, it follows 

wetted perimeter/ 

that the size of the sewer and the shape of the cross-section 
have considerable effect upon the velocity of a stream. The 

area 

maximum value of -:-- for a sewer flowing full is 

perimeter 

obtained, we learn from geometry, by making the cross- 
section circular; that is, for pipes of the same area, but differ¬ 
ent shapes of cross-section, flowing full, the circular gives the 
largest R. But this is not generally true when the sewer is 
not flowing full. 

If we examine the effect of depth of flow in a given cir¬ 
cular sewer upon the value of R we find that if the depth 

d — — (D equalling the diameter of the sewer) a = .3927Z?*, 

p — 1.5708/?, and R — 0.25 D. If the depth = D we find 
a = 0.7854Z? 2 , p = 3.1416/?, and R — 0.25 D as before. 


Table No. 13. 


d 

Depth. 

P 

Wetted 

Perimeter. 

a 

Area of 
Flow. 

R 

Hydraulic 

Radius. 

2 VR 

By Rutter's Formula. 

Corrected Propor¬ 
tional Velocities. 

Corrected Propor¬ 
tional Discharge. 

Full. 1.0 

3-142 

O.7854 

O.250 

1.00 

b 

0 

I .OOO 

0.95 

2.691 

O.7708 

0.286 

1 .07 

1.11 

1.068 

0.9 

2.498 

0-7445 

0.298 

1.09 

1 - 1 5 

I -073 

0.8 

2.214 

O.6735 

O.304 

1 . 10 

1.16 

0.98 

0.7 

I.983 

O.5874 

O.296 

1.08 

1.14 

O.84 

0.6 

1.772 

O.4920 

O.278 

1.05 

1.08 

0.67 

0-5 

I -571 

O.3927 

O.250 

1 .00 

1.00 

O.50 

0.4 

I.369 

O.2934 

0.214 

0.93 

0.88 

0-33 

0.3 

1.159 

O. 1981 

O.171 

0.83 

0.72 

0.I9 

0.25 

I.047 

O.1536 

O.I46 

0.76 

0.65 

O.14 

0.2 

O.927 

O. IIl8 

O. 121 

0.69 

0.56 

O.09 

0.1 

0.643 

O.O408 

0.0635 

0.50 

0.36 

O.03 




























7 o 


SE WEE A GE. 


As the depth of the sewage decreases from that of half the 
diameter the area decreases more rapidly than does the 
wetted perimeter, and consequently R decreases more and 
more rapidly as the depth diminishes. The above table 
shows this very plainly. The diameter is here taken as unity, 
the sewer circular. 

The formula for R for circular sewers for any given depth 
of flow is 



area 

wetted perimeter 


2 anr' x 

360 



sin a cos a 


2 a 
360 


X 2 nr 


y 


r 

2 


1 — 


180 sin a cos ci> 
an 1 


in which r — the radius of the sewer perimeter; 

a = the number of degrees in the angle whose cosine 
. r — the depth of flow 


For the egg-shaped sewer (see Art. 24) somewhat different 
values are found. 

Table No. 14 . 

EGG-SHAPED SEWER. 


(D = horizontal diameter ; H — vertical diameter.) 










d 

in parts 
of H. 

d 

in parts 
of D. 

P 

in parts 
of D. 

a 

in parts 
of Z> 2 . 

R 

in parts 
of D. 

1.8587 ^ R 

Corrected 

Propor¬ 

tional 

Velocities. 

Corrected 

Propor¬ 

tional 

Discharge. 

d 

in Circular 
Sewer 
in parts of 
D* 

Full 1.000 

1.50 

3-965 

I.1485 

0.2897 

I. OOO 

I.OO 

I.OO 

I.209 

0.667 

I.OO 

2-394 

0.7558 

0.3157 

I.045 

1.06 

O.69 

O.750 

0-333 

0.50 

1-374 

0.2840 

0.2066 

0.846 

0-77 

O.18 

0-354 

0.267 

O.40 

LI 59 

0.20485 

O.1768 

O.781 

0.70 

0.12 

O.284 

0.220 

0-33 

1.012 

0.15510 

0.1532 

0.727 

O.63 

0.08l 

0.228 

0.200 

O.30 

0.937 

O.13471 

0.1437 

O.704 

0.60 

O.064 

O.214 

0.133 

0.20 

0.706 

O.07497 

0.1062 

0.606 

O.49 

O.O30 

0.141 

O.067 

0.10 

0.463 

O.0279 

0.06026 

0-455 

0-33 

0.008 

O.O75 

0.033 

0.05 

O.321 

0.0102 

O.03177 

0.331 

O.23 

0.002 

O.O39 


* To give equal discharge in circular sewer of same capacity—i.e., one whose diameter = 
1.209 

































FLO W IN SEWERS . 




By Table No. 13 it is seen that when a circular sewer is 
half full the wetted perimeter and area of flow are each half 
of that for a full sewer. When the depth is but £ the 
diameter, however, the wetted perimeter is £, the area of flow 
less than £, and R about that of a full sewer; and when the 
depth is ^ the wetted perimeter is about £, the area T ^, and 
R about £ that of a full sewer. 

In the last two columns we have the proportional veloci¬ 
ties and discharges for various depths of flow, with allowance 
made for variations in c, calculated by Kutter’s formula, with 
sufficient accuracy for ordinary use. The fifth column shows 
proportional velocities if c is considered as not affected by 
changes in R. A comparison of the fifth and sixth columns 
shows the effect upon the coefficient c of variations in R } 
since if c — x for a full sewer for one .2 full it equals 
and for one .8 full ££|-.r. 

Reference to Table No. 13 shows that if, in a circular 
sewer with a depth of flow of £ the diameter, the velocity is 
i£ feet per second (the minimum velocity of flow ordinarily 
permissible for house-sewers), in the same sewer flowing full 
the velocity will be 2.3 feet per second. It also appears from 
this table that the greatest velocity is attained, not when the 
sewer is flowing full, but when the depth is .81 of the diam¬ 
eter, and that the maximum discharge occurs when the depth 
is .9 of the diameter. From this it follows that a circular 
sewer can never flow full unless under a head. 

The tables Nos. 11 and 12 for flow in sewers give the 
velocity and discharge for full sewers only, the velocity being 
the same for a sewer half full, while the discharge is one half 
as great. They do not give the maximum capacity of the 
sewer, which is theoretically 1.07 times that given; but the 
velocity and discharge for sewers flowing full are most con¬ 
venient for use and are on the safe side of exact accuracy. 

Where it is desired to obtain the- velocity or discharge of 


72 


SE WEE A GE. 


a sewer flowing partly full the tables can be entered with the 
quantities corresponding to the other conditions, the velocity 
or discharge of the sewer as if it were flowing full obtained, 
and such part of this taken as is indicated by the above table 
for the given depth. For instance, if it is desired to find the 
discharge of a io-inch circular sewer, grade I : 200, when the 
depth of flow is 0.4 the diameter, we find from the table that 
the discharge if running full would be about 650 gallons per 
minute; we multiply this by 0.33 and obtain 214 gallons, the 
volume required. Or, given the volume, 215 gallons, and the 
grade, I : 200, to find the depth of flow: we find the flow of 
a full sewer, 650 gallons, divide 215 gallons by this, obtaining 
and find the depth corresponding to this proportion of the 
discharge, or 0.4. 

The velocity obtained by the formula or from the table 
is that for a straight pipe of a uniform cross-section and 
condition of surface. In a system of sewers there are 
numerous curves, irregularities of surface, manholes, house- 
branches, etc., each of which may exert a retarding in¬ 
fluence upon the sewage. It is thought that there is no ap¬ 
preciable diminution of velocities in a curve whose radius is at 
least 5 times the diameter of the sewer. Weisbach’s formula 
for loss of head in curves is 

y CCL V 2 

h — - 

II 578 * 

in which c = .131 + 1.847^ ; 

r — radius of pipe; 

b = “ “ bend; 

a = angle in degrees; 

V — velocity in feet per second; 

h = head in feet necessary to overcome resistance of 
curve. 

From the above formula we find that if 



FLOW IN SEWERS. 


73 


r 

.3 .4 • 5 *7 *8 .9 1.0 

then 

^ = .131 -138 .158 .206 .294 .440 .661 .977 1.408 1.978 


As an example, assume a 10-inch pipe, or r = 0.42 feet, 
that b = 2 feet, that a — 90°, that V — 3 feet. Then h = 
. 138 X 90 X 9 

*-■—g-= .0097 feet, or less than •§■ inch. This result 

is not sufficiently large to materially affect the design. It 
represents the case of a junction between sewers made by a 
curve in a manhole (see Plate VIII, Fig. 5). This formula, 
however, does not apply to the foaming or impact created by 
an angle. A very considerable loss of head may result from 
this, and consequently sharp bends should be avoided unless 
it is desired to reduce the velocity. 

The obstructions to flow offered by manholes, house-con¬ 
nections, etc., can be almost entirely avoided by careful 
designing and construction. That due to roughness of the 
material of construction should also be kept low, but will 
necessarily be considerable. This obstruction should be 
allowed for in the formula by modifying the value of c through 
the different values of n. 


Art. 22. Limits of Velocity. 

The formula for the quantity of sewage which will flow 
through a given sewer per second is Q — Va, in which a is the 
area of the stream flowing. It would appear that, given Q , 
V and a could take any value so long as Va = Q. a is, how¬ 
ever, limited in its maximum by economic considerations, also 
sometimes by practical ones (see Art. 23). V also, although, 
if pure water were the material flowing through the sewers, it 
might vary from o to infinity, is limited within a compara¬ 
tively narrow range by the character of ordinary sewage. 

House-sewage contains some matter which is slightly 



74 


SE WEE A GE. 


heavier than water, also much which is lighter; the former 
tends to settle in the bottom of a sewer, the latter to collect 
along the edges of the stream. Ashes, garbage, clothing, and 
other refuse matter should be kept out of the sewers by laws 
rigidly enforced, but in spite of all precautions such material 
will at times reach them. Dirt and sand frequently enter 
house-sewers through the ventilation-holes in manhole-heads 
or through defective joints in the sewer. As no system is 
perfect or perfectly managed, provision should be made for a 
certain amount of such matter. It is found that if the 

i 

velocity of a stream be sufficiently great matter suspended in 
the water will not be deposited, but a retarding of the velocity 
at any point may cause a formation of deposits there. Ex¬ 
periments have been made to determine the velocities neces¬ 
sary for flowing water to render it capable of transporting 
matter of various sizes and densities, though usually earth, 
sand, gravel, and stones have been used. The results 
obtained by DuBuat are those usually quoted, and are given 
as being approximately correct for channels of uniform cross- 
section. The velocities are those sufficient to move the par¬ 
ticles along the bottom of the channel and are in feet per 
second. 

Table No. 15 . 

MATERIALS MOVED BY WATER FLOWING AT DIFFERENT VELOCITIES. 


Material. 


Bottom Velocity. 


Pottery-clay. 0.3 

Sand, size of anise-seed.0.4 

Gravel, size of peas.0.6 

“ “ “ beans. 1.2 

Shingle, about 1 inch in diameter. 2.5 

Angular stones, about inches in diameter. 3.5 


Mean Velocity. 
0.4 
0-5 
0.8 
1.6 
3-3 
4*5 


Other experiments have given slight variations from these 
figures, but they are sufficiently accurate for ordinary use. 
It must be remembered that they apply to loose material only. 
Where clay or sand has formed a compact deposit in a sewer 
many times these velocities may be required to move it. 
Just which of these or similar materials the sewage should be 








FLOW IN SEWERS. 


7 5 


given sufficient velocity to hold suspended is a question. 
But it has been found in practice that an actual velocity of i J 
feet per second will ordinarily suffice to prevent deposits 
where house-sewage alone is admitted. 

Where storm-water from the streets is admitted to the 
sewers clay, sand, gravel, leaves, etc., as well as lighter matter 
are washed through the inlets. The velocities in these sewers 
should be sufficient to prevent the deposit of such material, 
which velocity, according to the table given above, would 
needs be about 3.5 feet per second. 

The velocity given for house-sewers—ij feet per second 
—is that which should be maintained as a minimum by the 
ordinary minimum daily flow; that for storm-sewers—3.5 feet 
per second—is the least which should be attained in time of 
storms. 

The average daily flow in house-sewers may be taken 
(Art. 14) as of the maximum to be provided for, and the 
ordinary minimum as J of this. At night-time, when the 
absolute minimum usually occurs, the sewage is composed of 
comparatively pure water and a lessened velocity due to a 
shallower flow will not be particularly detrimental, f of the 
maximum volume for which the sewer is designed may there¬ 
fore be assumed as that for which the velocity should be 
1^ feet per second. For reasons to be given (Art. 23) a house- 
sewer is usually designed to be 50$ to 100$ larger than 
required by the assumed volume of sewage, so that the ordi¬ 
nary minimum can be taken as being \ to -J- of the capacity of 
the sewer. Reference to Table No. 13 shows that this 
quantity is carried when the depth of flow in the sewer is .25 
to .3 the diameter and when the velocity is .65 to .72 that 
for a sewer flowing full. It follows from this that the grade 
of a house-sewer should be such that the velocity when flow* 

1.5 1.5 

ing full is at least to —, or 2.3 to 2.1 feet per second. 


7 6 


SEWERAGE. 


In the case of storm-sewers, which carry no house-sewage 
and are thus dry for a large portion of the time, it may be 
assumed that in general any storm which will wash any con¬ 
siderable amount of gravel and dirt into them will require at 
least one third of the capacity of the sewer. Such grades 
should therefore be given these as will cause a velocity of at 
least 3.5 feet per second when the sewer is flowing one 
third full, or 4 feet when flowing full. Smaller showers, 
which will give less depth of water in the sewer, it may 
likewise be assumed will contribute only such matter as is 
transported by less velocities. 

It may in some cases be necessary to construct sewers 
giving somewhat lower velocities than these, but this should 
be only after careful consideration of the problem. House- 
sewers should never be designed with grades giving a less 
velocity than 2 feet per second when flowing full, nor storm- 
sewers with those giving less than 3 feet. 

Where a combined sewer is in question—i.e., one which 
daily carries house-sewage, but which also has sufficient 
capacity for and acts as a storm-sewer—the requisite velocity 
must be obtained for both house- and storm-sewage. But 
except in very unusual instances a grade which will meet the 
requirements of house-sewage will more than satisfy the 
demands of storm-water transportation. For, since the maxi¬ 
mum amount of house-sewage per second per acre in a resi¬ 
dence district will be about —-= .022 cubic feet. 

7.48 X 86400 ’ 

while the storm-water from such an area may be 3 cubic feet 
per second, or 140 times as great, if a circular sewer is 
designed to give a velocity of 1 \ feet when it is carrying .007 
of its full capacity its velocity when flowing full will be about 
9 feet, or more than twice the desired velocity; while with an 
egg-shaped sewer under the same conditions a velocity of 4.7 
feet when flowing full is obtained. 






FLOW IN SEWERS . 


77 


The subject of maximum velocities has received but little 
attention, probably because the dangers connected with 
excessive velocities are not so great as those resulting from a 
too slow rate. Such dangers do exist, however. The more 
immediate one is that the consequent shallowness of the 
current which would in many cases result would occasion the 
deposit of the larger floating solids, which may result in 
obstinate obstructions in the sewer. In the mains this can be 
obviated by reducing the size of the sewer to the point where 
the necessary depth is obtained. But it is usually not in the 
mains but in the branches that steep grades are possible. To 
reduce the sewer to such a size as would give any consider¬ 
able depth to the daily flow on very steep grades would call 
for a diameter much below that usually adopted as a mini¬ 
mum. An 8-inch sewer whose grade is o. i gives a theoretic 
velocity of 10.04 feet P er second when flowing full. To 
secure a flow in this pipe having an average depth of 4 inches 
would require the sewage from a population of 6500. In 
general it may be said that the ordinary depth of flow in any 
sewer should not be less than 2 inches, nor should it be 

4 

less than \ the radius of the invert, since if it is so there 
is much more danger of deposits forming along the edges 
and even in the centre of the stream. It will sometimes be 
impossible to meet this requirement fully, but it should be 
kept in mind as extremely desirable. 

Another objection to too great velocity is the danger of 
attrition of the sewer-invert by the scouring action of sand, 
stones, etc., swept rapidly over it. In brick sewers this 
objection is frequently and successfully met by lining the 
invert with granite blocks. A 5j-foot two-ring brick sewer 
in Baltimore, 25 years old, was recently found with its invert 
• in one place cut completely through for a width of 12 to 15 
inches and badly worn for a height of 2 feet, and many other 
places were only a little less damaged. In Omaha’s brick 




SE WEE A GE. 


sewers the wear, which is usually 18 to 24 inches wide, 
became 2 to 3 inches deep in 12 years. In both cities ordi¬ 
nary brick was used, but was replaced with stone blocks. 

The first objection is the serious one, since the time taken 
to wear out a sewer-invert must be considerable if good 
material is used, and replacing it is a matter of expense only. 
But the forming of deposits in the sewer endangers the health 
of the community. 

It is difficult to set a maximum limit to the velocity allow¬ 
able, but it may generally be taken as from 8 to 12 feet per 
second. From 3 to 5 feet per second is probably the most 
desirable velocity. 

Art. 23. Size of Sewers. 

If a house-sewer were constructed to exactly meet the 
theoretical requirements as above outlined it would contin¬ 
ually increase in size from the head to the outlet, by a small 
increment below each house-connection, by a larger one below 
each tributary branch or lateral; but between the first two 
connections it should be of sufficient size to carry the sewage 

b X 17 c 

of one house only, which would be about ---—- 

7.48 X 86400 

= .0016 cubic feet per second, which at a velocity of 2.5 feet 
per second would call for a pipe of .00064 square feet area, 
or ^ inch diameter. 

This method is not closely followed for the reasons that 
the data on which are based the calculations of volume of 
sewage as well as the formulas of flow cannot be exact enough 
to warrant it; that the estimate of ultimate population may 
be exceeded; that the per capita water-consumption may 
increase beyond the maximum assumed, factories or other 
large contributors of sewage locate at points where they were 
not expected, or for some other cause the amount of sewage 



FLO W IN SEWERS. 


79 


reaching any lateral may be largely exceeded. This excess 
can be allowed for in a general way only, but it is advisable to 
design the laterals of a capacity double that calculated, par¬ 
ticularly since the cost is not thereby largely increased, and 
the velocity in a sewer flowing half full is as great as that in 
one flowing full. 

The house-sewer mains need not have so great an excess 
of size, since they carry the sewage from many laterals, and 
it is not probable that all these will receive double the calcu¬ 
lated amounts of sewage. It will probably be sufficient to 
increase these by 50 $ of the estimated capacity. The volume 
of sewage reaching the trunk or outlet sewer can be still more 
closely calculated, and an increase of 25 % may be made as 
giving it sufficient capacity, although it would probably be 
better to add 50$ here also, the additional cost being slight in 
most cases. 

With this increase the head of each lateral would still be 
less than \ inch in diameter. This would be too small to 
adopt in practice for several reasons: because an individual 
house will contribute sewage at occasional maximum rates far 
exceeding 175$ of their daily average; because a very small 
sewer would be too frequently stopped by pieces of paper, 
or by other legitimate sewage matter; and because it would 
be too difficult of access for inspection and cleaning. The 
last two objections could, it is true, be met theoretically by 
making the house-connection of a size so much smaller that 
nothing could pass it which would obstruct the sewer. But 
such construction would be utterly impracticable. 

There is no particularly good reason, however, why a 
house-connection might not be made of 2-inch pipe and the 
sewer of 3-inch or 4-inch; and systems are in existence and 
reported working satisfactorily where such sizes are in use. 
But such construction would generally compel a change in the 
stock dimensions of all house-plumbing and connected appli- 


8o 


SEWERAGE. 


ances, and give rise to inconveniences more than balancing 
the saving in cost. A 4-inch house-connection is, however, 
ample for any building containing less than 50 persons and 
which contributes only ordinary house-sewage (see Art. 82). 

The sewer might, then, where the grade is quite steep, be 
constructed as a 4-inch pipe from the head to such point as 
the calculations fix for an increase in size; but it is better to 
make the minimum diameter 6 or 8 inches, for then there 
would be less probability that anything passing the house-con¬ 
nection, in which the velocity may be considerable, would 
obstruct the sewer. It is thought that the weight of evidence 
tends to show that with 4-inch house-connections 8-inch 
sewers are obstructed much less frequently than are 6-inch. 
Among other reasons for this is the fact that a 6-inch stick, 
chicken-bone, etc., will pass a 4-inch trap, but an 8-inch one 
will not; and that a 6-inch stick is more apt to become 
wedged across a 6-inch pipe than across an 8-inch one. Some 
engineers set the 6-inch, more, probably, the 8-inch pipe, 
as the minimum to be employed for sewers. In England 
9 inches is generally the minimum size. 

In the case of storm-sewers the only change of conditions 
affecting the volume of sewage which is likely to occur is in 
the imperviousness of the contributing area. If this is taken 
at the maximum, as for a business district, no allowance need 
be made. In any case the allowance for change can best be 
made in the selection of the factor of imperviousness and the 
sewer built of corresponding capacity. It is probable that no 
condition of size or character of tributary area will in actual 
practice call for a storm-sewer of a diameter less than 10 or 
12 inches. It should, if possible, be of a diameter at least as 
great as that of the largest opening in the storm-water inlets, 
to prevent sticks lodging across it. 

A circular or egg-shaped sewer is sometimes limited in size 
by the amount of covering necessary and the distance below 







FLOW IN SEWERS. 


81 


the street-surface of its invert, where this is fixed by the eleva¬ 
tion of the outlet and the necessary grade from that to the 
point in question. If the whole sewer at this point be lowered 
the grade and velocity become less and the size of the sewer 
must be increased, thus raising the crown.' The size can be 
reduced only by increasing the grade, which means raising 
the sewer. Under these conditions the sewer can be built as 
an “ inverted siphon ” to flow under a head (Art. 38), two or 
more parallel sewers can be substituted for the one, or the 
shape can be modified. In adopting the last alternative 
engineers have devised many forms which can be generally 
classified as those flattened on the bottom and those flattened 
at the top. 


Art. 24. Shape of Sewers. 

Of all possible shapes of sewers of equal area of cross-sec¬ 
tion the circular gives the greatest velocity when flowing full 
or half full and, having the shortest perimeter, contains the 
least material. Also, being devoid of angles, it offers little 
opportunity for deposits. For sewers intended to always flow 
at least half full it is therefore the most desirable shape. 
This is not true, however, of a combined sewer—that is, 
one which carries both house-sewage and storm-water— 
for, as we have seen (Art. 22), the house-sewage may occupy 
only of the capacity of the sewer and have a velocity only 
about ^ as great if a circular sewer be used. If the sewer, 
considered as a storm-sewer, be given a grade adapted to a 
velocity of 4 feet per second when flowing full or half full the 
velocity of the house-sewage would be about f of a foot per 
second. If on the other hand the grade be so increased 
(which is seldom possible) as to give the minimum house- 
sewage flow a velocity of 1J feet per second the depth of this 
flow would be only about .02 of the sewer diameter. Neither 
of these conditions is permissible in a good sewerage system. 



82 


SE WERA GE. 


The result of adopting too flat a grade is shown by the 
illustration (Plate VII, Fig. 8) of obstructions in the old 
London sewers, which came to be known as “ sewers of 
deposit.” These required frequent cleaning, since almost 
the entire sewage matter was deposited in them, and became 
very dangerous to the health of the city. The question thus 
forced upon the attention of engineers was first solved by 
building in the bottoms of the old sewers channels of much 
shorter radius of curvature (Plate VII, Fig. 7). These, by 
increasing R and consequently F, as well as the depth of flow 
relative to the invert radius, had the same effect upon the flow 



as the use of smaller sewers, which they in fact were, and 
answered the purpose, practically the same design being still 
employed in Washington, D. C., and other American cities. 
It will be noticed, however, that there is considerable useless 
material in this design; also that the bench on either side of 
the small channel offers opportunity for the deposit of 
material, which may there putrefy. To meet these objections 
the egg-shaped sewer was designed and is used extensively 
for combined, and often for storm-water, sewers. Several 







I 

FLOW IN SEWERS. 83 

proportions have been suggested and used, but that most 
frequently found in modern American practice is represented 
here. The diameter of a circular sewer having an equal area 
is 1.209 D. In this sewer 

H — 1.5 D, dc or r' =0.5 D, 

ef ox r = 1.5 D, gh or r" = 0.25 D. 

Reference to Table No. 14 shows that a flow of y^j- of the 
full capacity of this sewer would have a velocity about 0.3 as 
great as if the sewer flowed full, or 85$ greater than the same 
amount in a circular sewer of equal total capacity; also the 
depth would be about o. 1 D, or o.\r". If the velocity of the 
house-sewage in the above be 2£ feet per second (as it should 
be) that when the sewer were full would be 8 feet or more 
per second. This form does not, therefore, quite meet the 
requirements of a combined sewer, intended to carry a run-off 
of 3 inches from the area drained, as to either depth or 
velocity of house-sewage. As we shall see later, this require¬ 
ment applies to lateral combined sewers only, and this design 
is suitable for most combined-sewer mains, whose maximum 
flow is only ij or 2 inches run-off from the drainage-area. 
In laterals or other sewers, however, where the proportion ol 
house- to storm-sewage will be too small, or for some othei 
reason sufficient velocity and depth for the house-sewage 
cannot be thus obtained, the adoption of an egg-shaped sewei 
with r" = \D or \D, or a form similar to that shown in Plate 
VII, Fig. 2, is recommended, the purpose being, whatever 
the form adopted, to get a satisfactorily high value for R for 
the house-sewage flow. Whatever the radius of invert the 
grade must not be less than that which would be required 
by a circular house-sewer having a radius = r". The 
radius r" should be so chosen, also, that the depth of house- 

r" 

sewage will never be less than —. A flat bottom should 



SEWERAGE . 


84 

never be used for house or combined sewers unless the 
sewage will always be sufficient to cover it at least 6 inches 
deep. Angles in the section are to be avoided as favoring 
deposits. In storm-sewers it is advisable that the shape be 
such as to give good velocity to small amounts of storm¬ 
water, but the penalty of not following this rule is not so 
serious as in the case of house-sewers. 



CHAPTER V. 


FLUSHING AND VENTILATION. 

Art. 25. Necessity for Flushing. 

It is seen from Table No. 13 that if at any time the flow 
in a circular sewer becomes less in volume than T y ¥ the full 
capacity of the sewer the depth becomes less than J the 
diameter and the velocity less than § that for a full sewer. 
If the sewer is small the first condition is apt to cause 
deposits by the stranding of floating matter on the edges or 
even in the centre of the stream; if the grade is near the 
minimum the velocity becomes less than is desirable and 
deposits result from this cause. But a 6-inch or 8-inch pipe 
is usually the minimum size employed and is carried up to the 
last house-connection, from which a quantity of sewage very 
much less than y/y of the full sewer capacity is received. In 
fact there will be in a residence district a stretch of at least 
400 feet of 6-inch or 700 feet of 8-inch sewer, even at the 
flattest allowable grade, which would be filled less than y 1 ^ of 
its capacity by a rate of 175 gallons per capita, and conse¬ 
quently where deposits are probable. The discharge from any 
individual house comes usually not in a continuous flow, how¬ 
ever, but in spurts of relatively large quantities separated by 
considerable intervals of time. If we watch .such intermittent 
discharge we will find that when the sewage enters an empty 
sewer from the house-connection it flows both down the 
grade and also up it for a short distance. The latter portion 

85 


86 


SEWERAGE . 


at the end of the discharge also flows down grade, but it has 
probably carried with it and left at the upper limit of its flow 
matter which remains there to putresce and perhaps form the 
beginning of an obstruction. Beginning in the sewer at 
practically nothing (since most of the initial velocity is 
destroyed by foaming), the velocity of such discharge contin¬ 
ually increases, and the depth decreases, with the distance 
from the point of entry. This frequently causes the strand¬ 
ing below the house-connection of large floating matter which 
is introduced from such connection, and although successive 
discharges may move this matter, each one a little further 
down the sewer, a long cessation of them may give it an 
opportunity to become fixed in its position. Discharges from 
connections higher up the grade will tend to prevent these 
deposits, two or more discharges occasionally coming simul¬ 
taneously and uniting their volume; and generally the further 
any connection is from the upper or dead end of a branch the 
less the danger of its causing such deposits. In a thickly 
settled district this danger in the case of 6- or 8-inch pipe 
becomes very small at a point to which there is tributary 
iooo to 1500 feet of sewer. If the district is sparsely settled, 
however, the danger may exist for many times this length. 

Any house-sewer, but particularly a lateral, is liable to 
partial stoppage at times, due to ashes, sand, or other 
material introduced through house-connections, manholes, or 
infiltering through the joints or other defective places. 
Unless the velocity of flow is sufficient to carry this matter 
along it will form deposits in the sewer-invert which must be 
in some way removed. 

There is another class of deposits, composed of mycelial 
matter, which forms in most house-sewers. This contracts 
the area of cross-section and may become the breeding-place 
of micro-organisms; but emits little odor and is readily de¬ 
tached and carried away by a strong flush of water. 


FLUSHING AND VENTILATION. 


87 


To prevent these deposits the only practicable way known 
is to keep all sewers constantly flowing with a depth at least 
\ the radius of the invert, water being introduced for this 
purpose if necessary, and also to maintain a velocity of at 
least feet per second. To remove them the methods 
employed are either to occasionally turn through the sewer 
streams of water of sufficient quantity and velocity to dislodge 
and remove the deposits, or to employ shovels, hoes, 
“ pills,” scrapers, or similar appliances to be described in 
Chapter XV. 

The method of prevention, if applied near a dead end,, 
where the sewage flow is minimum in quantity, even in the 
case of a sewer laid at minimum grade, would require about 
47,000 gallons per day for each line of 6-inch pipe and 83,00a 
gallons for each 8-inch line. These quantities it will usually 
be impracticable to supply; and were it practicable the addi¬ 
tion to the sewage of this amount in each of several branches 
would compel a large increase in the size of the sewer-mains, 
and greatly increase the cost of treatment in case this method 
of disposal was employed. There will occasionally be in¬ 
stances, however, where a convenient stream of water can 
be utilized to advantage in this way. 

It sometimes happens that an old sewer-main or other 
large drainage-channel is at so flat a grade as to be, in part at 
least, a sewer of deposit. Flushing can be used to advantage 
in such a case to stir up and remove the matter deposited. 
A notable instance of this may be found at Milwaukee, Wis., 
where 40,000 gallons of lake-water per minute are pumped 
into the Milwaukee River (the flow of which is largely sewage) 
for flushing it. 

In general a sewer in which there is a continuous flow 
with a depth of at least £ the radius of the invert and a 
velocity exceeding 2 feet will need but infrequent cleaning if 
legitimate sewage only be admitted. If for any reason or at. 


88 


SE WE A AGE. 


any time these conditions be not fulfilled artificial cleaning 
will probably need to be resorted to. 

Art. 26. Methods of Flushing. 

As stated, there are two general methods of cleaning 
sewers: flushing, and by the use of some kind of scraper or 
similar tool. The latter usually calls for no special provisions 
in the construction and will be treated of in Part III. 
Flushing, however, is frequently accomplished by appliances 
built into the system, and the principles involved are other 
than those controlling hand labor; it is therefore necessary to 
consider it in designing. Flushing may be done by hand, by 
automatic appliances, or by use of rain-water. 

By the first the sewer can be flushed from any manhole, 
as well as from flush-tanks; by the second from fixed points 
only, usually the heads of laterals; by the third the flushing- 
water enters from roofs through all or many house-connec¬ 
tions, or In some instances the inlets are so constructed as to 
store the rain-water from the street-surfaces or from water¬ 
courses and flush with periodic discharges of the same. 

The secret of successful flushing lies in compelling a large 
mass of water to move at considerable speed down the sewer. 
If the sewer be less than 24 inches or 30 inches in diameter 
water should as far as possible completely fill it, that deposits 
may be removed from its entire circumference and also that 
the effect of the flush may be felt far down the sewer. With 
the sewer flowing full bore at the upper end the depth of the 
water will decrease as the flushing-wave progresses down the 
sewer, until at some point below, at a distance varying with 
the size and grade of the sewer, with the head of water at the 
upper end and the volume of sewage flowing, the depth and 
velocity of the sewage will be but little affected by the flush. 

The initial velocity will depend upon the head and upon 


FLUSHING AND VENTILATION. 


89 


the facility offered the water for entering the sewer. There 
should be a free and open orifice at the entrance end, and if 
possible the angle between the inside of the sewer and that 
of the manhole or flush-tank should be rounded. Speed is of 
as much value in flushing as quantity, and with a given 
amount of flushing-water the more quickly it can be made to 
pass through the sewer the better. In most cases little 
if any benefit would result should a faucet be left con¬ 
tinuously running in each house in a city, but T¥ Vo' ^ le 
same amount of water used in a proper way would be of great 
benefit to the system. 

Although for creating velocity the head in the flush-tank 
should generally be as great as possible, it must be limited by 
the amount of internal pressure which the sewer can stand 
without rupture. A few years ago a brick sewer in Washing¬ 
ton, D. C., was, on account of insufficient size, put under 
such a head of water by the run-off from a cloudburst that 
its upper half was completely severed from the lower and the 
sewer destroyed, and a similar result might follow from too 
great pressure of flushing-water. With a pipe sewer this 
danger is not so great. A head of 6 or 8 feet at the manhole 
or flush-tank—which is more than can usually be obtained— 
should not endanger a pipe sewer. Brick sewers as ordinarily 
constructed should not be filled to a point more than 5 feet 
above the invert or, for those more than 5 feet in diameter, 
higher than the crown. In no case should the water be 
backed up a sewer-line to such a height as would flood any 
connected cellars. 

The flushing-water should move down and not up the 
sewer, since the effect of the latter would probably be to 
sweep the intermediate deposits nearly to the upper limit of 
the wave and leave them there to dam the flow. The inter¬ 
val which should elapse between flushings will vary under 
different conditions. In sewers where there is a constant 


90 


SEWERAGE. 


ample flow of water, where stoppages are few and due solely 
to accident or design of ignorant or malicious persons, flushing 
need be resorted to only when such stoppages occur. If it is 
found from experience that stoppages are frequent or that 
there is a constant depositing of material in the sewers, or if 
it is foreseen that this will occur from causes mentioned in 
the previous article, frequent flushings should be provided for. 

In the case of a dead end of a house or combined sewer, 
or one which has but few house-connections made with it, the 
flushing should be done once in each 24 or at least 48 hours. 

Both separate and combined systems have been built and 
satisfactorily maintained without flushing at any point oftener 
than two or three times a year. It is probable that this is 
possible only where there is considerable ground-water enter¬ 
ing the sewers at their upper ends, or where the dead ends 
occur only in thickly populated districts and on grades a 
little greater than the minimum herein advocated. There is 
too little definite information on this subject to justify a posi¬ 
tive statement as to when, if ever, flushing at dead ends may 
be profitably omitted. It is advisable so to anange every 
house or combined sewer, where the conditions will be those 
given as favoring deposits, that it can be satisfactorily flushed. 

A few experiments have been made on the actual effect 
of flushing-water in a sewer, chiefly with reference to the 
velocity and depth of the flushing-water at different distances 
from the point of entering. Andrew Rosewater found by 
•experiment with a 4°°-gallon tank at the head of an 8-inch 
line of sewer discharging 11 gallons per second that at the 
first manhole, 200 feet below the flush-tank, the water was 
6 inches deep and had a velocity of 5.6 feet per second; 200 
feet further the depth was 5 inches, velocity 2.8 feet; and 
400 feet further the depth was 4 inches, velocity 2 feet— 
showing the flushing effect to be practically exhausted in 800 
feet. Mr. Ogden, in experiments made in Ithaca, N. Y., 


FLUSHING AND VENTILATION. 


91 


in 1897, found that with discharges from flush-tanks through 
8-inch pipes of from .89 to 1.1 cubic feet per second the flow 
was reduced to 2 inches at 1123 feet from the flush-tank in 
two cases where the grades varied from .52# to 1.31$, at 
about 1000 feet in another where the grades varied from 
1.02$ to 3.14,^, and in another where the grades varied from 
.80$ to .89% the depth was 4 inches at 895 feet from the 
flush-tank. In the first two the sewer was scoured clean for 
529 feet and some effect felt at 819 feet; in the third the 
sewer was cleaned for 556 feet and the effect slight at 970 
feet; in the last the pipe was “ disturbed, but not cleaned,” 
at 636 feet, until 600 gallons were discharged, when it was 
cleaned for more than 636 feet, but less than 900 feet. The 
other discharges referred to were of 300 gallons each. An 
interesting series of experiments were conducted and their 
results plotted by S. H. Adams in England. These appeared 
to show, as do the above, that 300 gallons is in some cases 
insufficient to properly flush an 8-inch pipe; also that the 
effect of such a quantity is felt for about 800 to 1000 feet.* 

In flushing by hand the sewer is usually stopped at the 
down-grade side of a manhole or flush-tank, this is filled to a 
desired height with water or by allowing the sewage to 
accumulate in and above it, the gate, plug, or other stopper 
is removed and the water allowed to enter the sewer under 
the head due to its height. Where outside water is used for 
flushing and is limited in quantity another stopper should be 
placed at the upper orifice in manholes, to prevent a flow up 
the sewer, and left in until the flushing is over. The stoppers 
are made of various forms and to act in various ways, and to 
close the whole or only the lower half or two thirds of the 
sewer. The water is obtained from different sources and 
introduced by different methods, a further discussion of which 
will be given in Part III. 

In England the separate system, when first constructed, 

* See also Transactions Am. Soc. C. E., vol. XL, pp. 1-30. 


9 2 


SEWERAGE. 


was designed to admit to the house-sewers roof-water and 
drainage from yards, and this method is still followed there 
to a considerable extent. In the United States the majority 
of separate systems are not supposed to receive this water. 
It is argued by advocates of the former practice that the 
householder should not be required to construct two connec¬ 
tions, one for house-sewage and one for rain-water. But the 
last can be conveniently discharged into the gutter, except 
in the case of buildings covering a large area, when the cost 
of the extra drain would be relatively inappreciable. 

Another argument for the admission of roof-water is that 
it is beneficial in flushing the sewer. If it is admitted only 
at and near the dead ends it will usually be advantageous, but 
it should not be thought to take the place of all other flush¬ 
ing. The sewers are most likely to need flushing at dry 
seasons, and this must then be done by hand or otherwise. 
There is a danger that the presence of these roof-connections 
will give a false idea that the flushing requirements have been 
entirely met. 

If roof-water is admitted to small sewers throughout their 
length there is great probability of its gorging the pipes and 
backing up into connected basements and cellars. In Mount 
Vernon, N. Y., in 1892 great damage was caused in this way 
and all roof-drains were at once disconnected; and many 
similar instances might be cited. 

Since the danger is so imminent and the benefits con¬ 
tributed at such uncertain intervals, most American engineers 
do not advise the admission of roof-water to small sewers. 

Sewers are sometimes flushed by connecting their upper 
ends with convenient streams, or artificial channels filled from 
such streams, the water being admitted periodically by gates: 
as at Bern, Wurzburg, Innsbruck, Freiburg, Breslau, Munich, 
and other cities of Europe; also at Newton, Mass. 

Reservoirs fed by streams or springs are used in Munich, 


FLUSHING AND VENTILATION. 93 

Cologne, Wiesbaden, Frankfurt, Stuttgart, and other cities. 
At the first-mentioned place large underground reservoirs, one 
of which is 6 feet 6 inches by 4 feet 7 inches and extends along 
two blocks, are filled from the Isar River. 

Tides are sometimes made use of for this purpose, the 
water being allowed to rise in the sewer at high tide and 
being held there by gates until the low tide, when it is 
released. Ordinarily only the lower reach of the outlet sewer 
can be thus flushed. A better method in some cases is to 
hold the water after high tide in a basin from which it is 
rapidly discharged at low tide into the sewers to be flushed. 

As in the case of Milwaukee, already cited, and of Bre¬ 
men, the flushing-water may be pumped from a lake or river 
directly to the sewer. This is of course applicable within the 
limits of economy to very large sewers only, or to a system 
where a number of dead ends can be reached by a compara¬ 
tively short line of water pipe. 

The water for flushing is sometimes taken from the ocean 
or other body of salt water; but the salts are thought to 
decompose the sewage, giving rise to gases and deposits of 
matter rendered insoluble, and are corroding to any metal¬ 
work in the sewers. Hence its use is not advised by most 
authorities. 

Art. 27. Appliances for Flushing. 

Automatic flush-tanks are in use in a large number of sep¬ 
arate systems, but are seldom used for flushing combined or 
storm-water sewers, owing to the enormous quantities of 
water needed for that purpose. There have been a great 
number of devices invented for flushing. Most of those at 
present used in any considerable numbers are siphons in prin¬ 
ciple, so arranged that a tank in which they are set may fill 
gradually up to a certain point, when its contents are dis- 


94 


SE WEE A GE. 


charged rapidly into the sewer. The tanks are made to con¬ 
tain at the time of discharge from 150 to 600 or even 1200 
gallons for 6- to 10-inch pipe sewers. Tor larger sewers larger 
quantities are provided. The smaller quantities are of little 
use. No tank should discharge less than 250 gallons at a time 
into a 6-inch pipe, and correspondingly larger amounts into 
larger sewers. 500 to 800 gallons discharged into an 8-inch 
pipe once in 24 hours would be more beneficial than half of 
that amount at each of three or four discharges during the 
same time. It is probable, however, that in sewers calculated 
for a velocity exceeding 5 feet per second equal efficiency may 
be obtained with quantities less than those stated. 

The tanks should, of course, be water-tight. They are 
usually built of brick plastered on both the inside and the out, 
but might be made of wood or of iron. They should be so 
built and arranged that the water may have the greatest per¬ 
missible head above the sewer when discharging. (For details 
see Art. 47.) 

The water may be conveniently admitted to the tank 
through a half-inch or smaller stop-cock connected with the 
street-main by a supply-pipe passing through the tank-wall. 
This cock is continually left sufficiently open to cause the 
tank to fill and discharge at desired intervals. If the water is 
inclined to be muddy at times the use of too large a supply- 
pipe will result in the choking of it by sedimentation. It 
should be of such a size that the quantity to be used in the 
tank will pass through it with a velocity of 2 feet per second 
or more. 

The discharge-pipe of the tank should be at least as large 
as the sewer. It would be better to have it a size or two 
larger and bell-mouthed at the end, but this is seldom 
done. 

The automatic flushing appliances most in use in the 
United States are further referred to in Chapter VIII. They 


FLUSHING AND VENTILATION. 


95 


are, most of them, covered by patent, and the prices range 
upward from about $12 fora tank to discharge 150 gallons 
through a 5-inch pipe. 

Where automatic flush-tanks are not used some engineers 
have built into manholes at dead ends 2-inch to 4-inch pipes 
connected with adjacent water-mains and provided with gate- 
valves, as at Mount Vernon, N. Y., and Newton, Mass. 
This is probably the most convenient method of hand-flushing 
and the cheapest to operate. The cost at Mount Vernon was 
about $40 for each 4-inch branch and connection. 

There are numerous methods of flushing by hose, by 
water-tanks, etc., many of which are described in Part III. 

In flushing by rain-water no special appliances are ordi¬ 
narily used, the roofs and sometimes the yards being con¬ 
nected in the ordinary way with the sewer. 

Special methods involving pumping, some instances of 
which have been referred to, need no description, since the 
details will vary with each case. 

Art. 28 . Necessity for Ventilation. 

In every sewer there is a space above the sewage filled 
with air, and this air, it is evident, will generally be far from 
pure unless kept in motion and frequently renewed. The 
odor accompanying all sewage, even when there is no decom¬ 
position proceeding in the sewer, is communicated to this air; 
there will frequently be given off some gases due to putrefac¬ 
tion; and it is possible that malefic germs may escape in 
vapor from the sewage or from deposits in the sewer, to be 
carried along by the air-currents. This air probably is seldom 
motionless. It is influenced by the sewage to move down the 
sewer; it is warmer in winter and often in summer than the 
outside air, which condition occasions motion when there is 
communication between the two; it is driven out of or along 


9 6 


SEWERAGE. 


the sewer by sudden inflows of sewage from house-connections 
or branches and sucked in by decrease in the volume of flow; 
near the outlet the direction and force of the wind affect it, 
driving it up the sewer or sucking it out; last, and most im¬ 
portant, it passes into empty or partly empty house-connec¬ 
tions and into proximity to, if not into the air of, connected 
residences. Herein lies the danger. There is no “ sewer- 
gas ” which is deadly to human life, but it is known that air 
which has been confined in contact with decomposing sewage 
is charged with ” an ever-varying mixture of gases; and of 
those that are deleterious the more prominent are sulphuretted 
hydrogen, sulphide of ammonium, and caburetted hydrogen; 
while ammonia, carbonic acid, and occasionally carbonic oxide 
derived from leakage of illuminating-gas into sewers are 
present in more or less large proportions.” (W. P. Gerhard, 
“ Sanitary House Inspection.”) 

The least that can be said of these is that they lessen the 
vitality and prepare the way for easy conquest by diseases 
that might otherwise obtain no hold upon the system; they 
should therefore be excluded from all occupied buildings. 
The danger due to impure air in dwellings has led the New 
York Board of Health to conclude that “ 40 % of all deaths are 
caused by breathing impure air.” Playfair asserts that in 
modern hygiene “ nothing is more conclusively shown than 
the fact that vitiated atmospheres are the most fruitful sources 
of disease.” Death rates have been “ reduced in children’s 
hospitals from 50$ to $% by improved ventilation.” 

While the vitiation referred to in these quotations is not 
that of sewer-air exclusively, this is included among the 
causes of it. and produces the same effect. Unfortunately the 
most numerous and fruitful sources of the gases are found, 
not in the sewer, but in the house-connections or soil-pipes, 
and consequently not directly under the control of the 
authorities. The methods necessary to prevent danger from 


FLUSHING AND VENTILATION. 97 

these sources will be considered under the head of House- 
connections (Art. 82). 

Art. 29 . Methods of Ventilation. 

It is evident that the danger from sewer-air may be 
avoided, or at least lessened, in two ways: by preventing the 
creation of gases, and by preventing the sewer-air from reach¬ 
ing human beings in dangerous quantities or under dangerous 
conditions. No method has yet been found for perfectly 
accomplishing either of these aims in practice, but both may 
be partially attained. 

Aside from illuminating-gas most of the objectionable 
gases are given off by putrefaction, and the prevention of this 
in the sewers is therefore most necessary. This is best 
accomplished by the removal of all sewage to the outlet before 
putrefaction can begin; and here is seen the advantage of 
daily flushing, cleaning the upper laterals of deposits before 
they reach this dangerous stage. The use of disinfectants in 
sewage for this purpose is seldom advisable, both on account 
of the enormous cost and practical difficulties of applying 
them and because the various and changing characters of 
sewage in different cities and from hour to hour may intro¬ 
duce such matter as will combine with any given disinfectant 
to produce deposits and gases fully as injurious as those due 
to sewage alone. The transporting of germs by sewer-air is 
probably reduced by reducing putrefaction, although there is 
very little definitely known on this point, it being uncertain 
even whether disease-germs are carried by sewer-air at all. 

To prevent air from the sewer from entering houses two 
general methods are in use: placing a barrier in the house- 
connection, and removing the sewer-air through other outlets. 
The former is one of the aims of the plumber and is usually 
attempted by the use of traps. The latter has been aimed at 


9 8 


SEWERAGE. 


by the use of many ventilating devices, in few or none of 
which has positive action been successfully obtained. A 
combination of these two methods gives reasonably good 
results in most cases, a partial obstruction to the air being 
placed in the house-connection or its branches in the shape 
of water-sealed traps, and the power of the air to force its 
way through these being lessened by ventilation. 

If the sewer were a tight conduit with no inlets or outlets 
except through the house-connections and the main outlet 
the sewer-air must remain constantly unchanged and stagnant, 
or must find exit and entrance through these house-connec¬ 
tions. The first condition is impossible, for the amount of 
sewage varies from hour to hour and must displace and in turn 
be displaced by air driven to and derived from some outside 

source. In case of a sudden discharge of sewage into such a 

; 

sewer the air will be driven through the only outlets—the 
house-connections—unsealing the main traps, and the second¬ 
ary ones also unless these be amply vented. A strong wind 
blowing up the sewer from the outlet may produce the same 
result. In addition to other ventilation of both sewer and 
soil-pipe it is therefore advisable to thoroughly vent all house- 
traps. 

Attempts have been made to constantly remove the air 
from sewers by either sucking out the foul air or forcing in 
fresh; that is, by producing a current through the sewer to a 
given outlet by either the vacuum or plenum process. Both 
have proved failures as well as very expensive. In no experi¬ 
mental case has the effect been felt more than 1000 feet from 
the fans or other apparatus, not only on account of the great 
amount of air in the sewer-mains and laterals to be moved, 
but because the traps in the house-connections were unsealed 
by the pressure and air admitted from or forced into the 
buildings, according to the system employed. 

The Metropolitan Board of Works, London, concluded. 


FLUSHING AND VENTILATION . 


99 


after exhaustive study of the question, “ that the method of 
ventilation adopted in mines, where there are only two open¬ 
ings to be dealt with (an inlet for the air at one end and an 
outlet for it at the other), is inapplicable to sewers.'’ This 
characteristic of a sewerage system renders impracticable all 
methods of ventilation depending upon one or two ventilators 
to each line of sewers: such as connecting the sewer-end with 
a chimney, which would afford little more ventilation than an 
untrapped soil-pipe at the same point or a special ventilating- 
manhole. 

Many expedients for ventilation have been devised and 
tried—among them connecting the sewers to street-lamps, 
where a suction is caused and the gas burned by a constant 
flame; placing in the crown of brick sewers small perforated 
pipes connected with “ uptake-shafts,” expected to cause a 
continuous removal of the gases; leading pipes from the 
sewer to special flues constructed in houses, within the body 
of the walls, adjacent to the chimney, or upon the outside of 
the house and running up above all windows; leaving the 
main house-drains untrapped and extending them above the 
roofs; placing flap-doors in the sewers, opening downward for 
the sewage, but closed to air, which can escape through open¬ 
ings just above such flaps; placing in the street centre at 
intervals along the sewer manholes or other ventilating-shafts 
with perforated covers; connecting the sewers by untrapped 
pipes with street-inlets at the curb line. In connection with 
these charcoal and other deodorizers are sometimes placed at 
the air-outlets. (See “ General Conclusions, Metropolitan 
Board of Works,” London.) 

There seems to be evidence in favor of the conclusion that 
the greatest danger exists in the house-connections themselves 
and not in the sewers, although the latter should be prevented 
from contributing to this danger. Of many analyses of sewer- 

air made not one to the author’s knowledge has shown a 

L. of C. 


IOO 


SE WEE A GE . 


greater impurity than that in a crowded city street, whether 
CO,, oxygen, or bacteria be taken as the basis of comparison. 
Equally positive proof goes to show that the average house- 
connection or the adjacent soil near open joints in the same 
does give rise to dangerous gases. (It is probable that the 
upper ends of branch sewers, if not flushed well and often, are 
open to the same charge.) However, a rush of comparatively 
pure air from the sewer forced through the traps of a foul 
house-connection is as objectionable as though it itself were 
polluted, since it forces into the building the impure air exist¬ 
ing in such connection. The vents on all traps should hence 
be of such capacity and so placed as to give full and imme¬ 
diate passage to all the air necessary to prevent forcing or 
siphoning of traps. 

This fact, that the house-connections themselves are fully 
as foul as, if not more so than, the sewers should be more 
generally recognized and better provision made for ventilating 
them. This is reasonably well done by placing a vent-shaft 
just above the main trap, continuing the soil-pipe above the 
roof and venting each trap throughout the house. But a still 
better circulation of air is obtained by omitting the main trap 
altogether and permitting the air from the sewer to pass 
through the house-connection unobstructed. The danger of 
this air passing the traps on house-fixtures is no greater than 
that of the soil-pipe air doing the same, and in the majority 
of cases the sewer air is the less dangerous. Such construc¬ 
tion is also of great assistance in ventilating the sewer. If 
only an occasional house-connection be left untrapped, how¬ 
ever, the odors from this may be objectionable, the sewer air 
being but little diluted by the infrequent openings. But the 
author knows of no city which makes this method compul¬ 
sory in all connections where it is not perfectly satisfactory. 
(See also page 344; and Appendix No. 1.) 



% 


FLUSHING AND VENTILATION. 


IOl 


The use of street-lamps as outlets may be advantageous, but 
the electric light has rendered argument for and against this plan 
obsolete. The use of hollow electric-light poles has recently 
been introduced in Columbus, O., with what success it is too 
early yet (1899) to state. The use of flap-doors in the sewers 
presupposes a regular flow of air in a fixed direction through the 
sewer, which investigation has found does not ordinarily exist; 
this, however, may be advantageous on steep grades, where 
there is a tendency for the air to rise past intermediate venti- 
lating-points to the highest ones. Ventilation through man¬ 
holes and other ventilating-shafts most, if not all, engineers 
recommend, although many do not consider these sufficient. 

The use of storm-water inlets for this purpose is much 
opposed by many, who contend that the sewer-air should not 
be discharged so near to passers-by upon the sidewalk. In 
fact this same argument is used by a few against ventilation 
through manholes in the centre of the street. It is probable 
that the danger from this cause is very slight, if it exists at all, 
since it is dependent, not upon the gases, which are enor¬ 
mously diluted upon reaching the outer air, but upon the 
presence of disease-germs in the exhalations, which is not 
proven. Moreover, the average catch-basin, even if just 
cleaned (as this cleaning is ordinarily done), is more offensive 
than any rightly designed sewer is at all likely to become; and 
it is extremely doubtful if, in connection with its odors, any 
contribution of air from the sewer could be detected. For 
these reasons it seems to the author desirable to connect the 
sewer with the street-inlets by ventilating-pipes and to place 
manholes with perforated heads at intervals. Since the 
latter are apt to be sealed in winter by ice and snow, and in 
summer by mud, the additional ventilation through the street- 
inlets would seem to be advisable, particularly if the sewer be 
not ventilated through the house-drains. A small amount of 
snow will not ordinarily stop the openings in a manhole-cover, 


102 


SEWERAGE. 


owing to the warm air of the sewer, but a heavy storm or 
frozen mud may easily do so. 

Since the proportion of air in a small sewer to the dis¬ 
charge into the same is much less than in the case of a large 
combined sewer, and consequently the effect of a given dis¬ 
charge is a greater compression of, and pressure transmitted 
by, the air in the smaller sewer, the sewers of the separate 
system need ventilation or safety-vents even more than do 
those of the combined. In case there are storm-water inlets 
to which ventilation-pipes from house-sewers may be led this 
method may be adopted; but ventilation through untrapped 
house-connections is probably more efficient. This extra 
ventilation is very often—perhaps in the majority of cases— 
neglected, but such omission is undoubtedly attended with 
danger. 

For house-sewers, ventilating manhole-heads and un¬ 
trapped house-drains; for combined sewers, these with the 
addition of untrapped street-inlets; and for storm-sewers, 
manholes and inlets—these, with flap-doors on steep grades, 
seem to the author the best methods so far devised for ven¬ 
tilation; and without ventilation any system will almost surely 
become a nuisance and a danger. The aim should be to se¬ 
cure by whatever method the greatest possible number and 
freedom of communications between the sewer and the outer 
air; and there is little doubt but that when this is realized 
the sewer air becomes so diluted and the organic matter float¬ 
ing in it so oxidized as to render it less dangerous and objec¬ 
tionable than the air of a crowded church or theatre. When 
this is not true the sewers are probably in great need of clean¬ 
ing and flushing. (See Appendix No. I for data on this 
subject.) 


CHAPTER VI. 


COLLECTING THE DATA. 

Art. 30. Data Required. 

Any plans made before the full and complete data are at 
hand may be shown by further information to be inadvisable, 
while their very existence may create a prejudice against the 
substitution of more efficacious ones. Therefore, although 
the development of the plans may suggest the desirability of 
further data the necessity for which was unforeseen, as much 
as seems necessary in this line and that of surveys should be 
done preliminary to any designing. 

The first necessity will be for a map of the district under 
consideration. This will usually include the city or town 
and all land over which it may spread in the future; also all 
adjacent areas which shed their water into or across the sur¬ 
face of this territory. This map should show all streets, lanes, 
etc.; all parks or other areas permanently devoted to vegeta¬ 
tion; all rivers, creeks, ponds, or other bodies of water—in 
fact all natural and artificial divisions of the area embraced by 
the corporate limits. It usually happens that this much can 
be found already mapped for other purposes; but unless it is 
known that the measurements from which such map was pre¬ 
pared were accurately taken a sufficient, number of check 
measurements should be made to establish its accuracy or the 
reverse. On the point of accuracy a question may arise as to 

how exactly the measurements should be taken. If these 

103 


104 


SE WEE A GE. 


should involve an error of no more than . 2 % they would be 
sufficiently accurate for the work in hand. For, as sewer 
grades are ordinarily run from manhole to manhole, and these 
are about 300 feet apart, an error of .2^ would mean that of 
.6 foot in that distance, which on a grade of (a fairly 
steep one) would involve an error in grade of .003 foot, which 
is much less than the least which could be expected in the 
construction of the sewer. 

It will be advisable to obtain also the location of all street- 
railroads, and of all gas- and water-pipes, their distance from 
the curb or side lines of the street and the depth of the 
pipes being noted. Also the location, grade, size, and con¬ 
dition of any existing sewers and appurtenances should be 
ascertained, by actual inspection if possible. 

The data for computing the extent of tributary drainage- 
areas will ordinarily need to be collected in their entirety, as 
it is seldom that such information exists in a serviceable form. 
The topographical surveys which have been made of several 
of the States, however, may be used to great advantage in 
this connection. The data desired includes the boundaries 
of the watersheds whose run-off does not reach a confined 
channel before entering the limits of the territory to be 
sewered. (Such water as passes through this territory in the 
form of streams rather than flowing over the ground does not 
affect the problem, unless these streams are to be walled in, 
in which case each one will form a problem by itself.) Also 
the slope of the ground and the character of the soil as to 
permeability should be ascertained, the location and extent 
of rock at or near the surface, of woods and of orchards. 
Care should be taken to note and locate any slightly worn 
channels along which storm-water ordinarily flows to the 
nearest creek or rivulet across territory not yet built up, as 
these, if they cross into the sewer district, indicate the points 
at which the storm-water must be intercepted. 


COLLECTING THE DATA . 105 

Such levels must be taken as are necessary for the plot¬ 
ting of profiles of each street, alley, or any other surface under 
which a sewer is.to run, including a profile across the. bed of 
each stream crossed, with the elevation of high- and low-water 
marks; also the elevation of the body of water into which 
either the crude or purified sewage is to be discharged, the 
elevation during drought and flood as well as the ordinary 
elevation being ascertained. The depths must be obtained 
of all cellars whose bottoms are not evidently above the grade 
of the proposed sewer, unless all sewers are to be placed at a 
fixed minimum depth, which is to be increased only by the 
demands of the necessary sewer grades and not by the depth 
of any cellar or basement (see Art. 37). Also if grades have 
been adopted for any street, but not yet carried into effect, 
these as well as the existing surfaces should be obtained. 

If a d isposal-ground is to be used for filtration or irriga¬ 
tion a dareful levelling of its entire surface must be made, 
and test-pits sunk to ascertain the character of the material 
to a depth of 5 to 8 feet. 

If it is considered desirable to discharge the crude sewage 
into a given body of fresh or salt water careful search should 
be made for the point best suited for the outlet; also in case 
of a river whether the dilution afforded in time of drought 
will be sufficient to prevent a nuisance. For this purpose the 
action of currents, tides, and prevailing winds should be 
investigated. Gaugings of the discharge of streams should 
be made, and inquiry as to whether and at what points further 
down the river the water is used for a public supply. It is; 
well also to have analyses made of river-water taken at inter¬ 
vals below the proposed outlet for use in possible suits against 
the city for nuisance; this whether or not the sewage is to 
be treated. 

The engineer should in person pass through every street 
in the district to be sewered, noting the character of each, the. 


SEWERAGE. 


lob 

location of the business and factory districts, the general 
character of the pavements and yards, and the average size of 
lot occupied by each residence. He must also ascertain as 
nearly as may be the present population and its past rate of 
increase; the probable direction and extent of the future 
growth of the business part of the city, as well as of the city 
as a whole. He should obtain the figures, if they exist, of 
water-consumption in this and neighboring cities; also all 
possible data concerning the rainfall. 

A considerable amount of other information will in many 
instances be desirable, called for by the peculiarities of each 
case. Many items, such as cost of materials and labor (for 
use in the estimate), will suggest themselves as they are 
. needed. 


Art. 31. Surveying and Plotting. 

Since extreme accuracy is not necessary in the transit 
survey, the use of the ordinary stadia methods will be found 
advantageous for either check or original surveys. Stadia- 
hairs in the level, for use in running street-profiles, will be 
found to expedite this work, and will permit reducing the 
number in the level party to two. The adjustment of the 
stadia-hairs should be frequently checked. 

The tributary drainage-areas will not need to be surveyed 
in great detail. If the natural features are boldly accentuated 
it may be sufficient to locate by a transit-line the limiting 
summits and ridges, both main ridges and spurs. If the 
country is gently rolling or generally flat contour surveys 
should be made of the whole drainage-area, or at least of any 
portion of it the disposal of whose run-off may offer difficul¬ 
ties. 

Of such undeveloped areas as may be reached by the city 
in its future growth and which will be embraced in drainage- 
areas for which sewers are to be at once designed accurate 


COLLECTING THE DATA. 


107 


contour surveys should be made, contours being located from 
I to 25 feet apart vertically, according to the nature of the 
country. They should be sufficiently close to show the con¬ 
figuration of the ground in considerable detail, but not so close 
that the contour-lines will obscure all else upon the map. 

Most cities and towns of any size have the street grades 
established and recorded with their profiles. An extensive 
experience in attempts at the adaptation of such information 
to the requirements of sewer-designing has demonstrated that 
in nine cases out of ten it is waste of time to attempt to use 
these records and profiles. For the levels have usually been 
taken by a succession of surveyors of varying degrees of 
efficiency; occasionally also the grades have been altered on 
the ground, but not upon the profile; and the time employed 
in discovering and rectifying errors and omissions would 
generally have sufficed for taking entirely new levels. 

The levels of the street-surfaces taken for the profile 
need be to tenths of a foot only, but the bench-marks and 
back- and fore-sights should be to thousandths. Readings 
should be taken along each proposed sewer-line not more than 
IOO feet apart, at every pronounced change of grade and at 
street intersections; the elevation of rails where the line 
crosses a railway, and at stream-crossings the profile of the 
bottom and the water-surface, should be obtained. 

A convenient scale for a map of a village or borough is 
200 feet to I inch, but if its size is such that this scale would 
necessitate the use of paper more than 3 feet wide it may be 
better to use a scale of 250 or 300 feet to 1 inch. It is inad¬ 
visable to use a smaller scale than this, and if the resulting 
map is still too large for the paper it may be necessary to 
spread it over two or more sheets. In such a case it will be 
found convenient, where conditions permit of it, to so arrange 
the sheets that each drainage-area shall appear upon one sheet 
only. Upon this map should be shown the location of 


io8 


SEWERAGE . 


the proposed sewers and all appurtenances, these being 
usually in red. 

A convenient scale for the profiles is 25 feet to 1 inch 
horizontal and 5 feet to 1 inch vertical. These should show 
the sewer-line at its proper grade, the depth of all unusually 
low cellars, the location of all manholes and other appurte¬ 
nances. A plan of the street is usually placed under the 
profile, showing the location therein of the sewer-line and all 
appurtenances. 

For ascertaining the best location for an outlet into tidal 
waters the use of floats is desirable, since thus can be learned 
the ordinary periodic movements of the water into which the 
sewage is to be discharged, and hence the possibility of the 
creation of a nuisance thereby. These floats should expose 
as little surface to the wind as possible. A pine rod or tin 
tube, weighted at the botom and with a numbered flag 
fastened to the top, is usually employed. They should be 
started at different stages of the tide from each point which 
is being considered as a possible outlet. Account should be 
kept of and allowance made for winds during the times the 
floats are in the water. Each float should be numbered and 
a record kept showing the time and place at which it was put 
into the water, the state of the tide, wind, etc. By means 
of one or more boats they should be so traced that the path 
of each can be plotted upon a map until it strands or passes 
beyond the point where sewage can create a nuisance. It 
may at times be necessary to follow a set of floats night 
and day for three or four days; seldom longer than this, for 
if they have not in that time passed to a considerable distance 
from the starting-point such point is not suitable for an 
outlet. 

The quantity of water flowing in a given stream and the 
resulting dilution can be ascertained by the use of floats or a 
current-meter, the cross-section of the stream being first 


COLLECTING THE DATA. 


IO9 


obtained. In some cases this flow can be obtained from 
government or State records of gaugings. If possible a gaug¬ 
ing of the stream during a drought should be obtained, since 
it is even more important that there be the necessary dilution 
at such a time than when the river is high. 

It is sometimes desirable to sink test-pits or bore at inter¬ 
vals along the line of each proposed sewer to ascertain the 
character of the material to be excavated. This is unneces¬ 
sary where cellars or other excavations along the street-line 
have been sunk to practically the depth of the sewer, and 
when neither rock nor quicksand is anticipated it is seldom of 
a service commensurate with the cost. In sounding for rock 
several methods have been used. 

An iron rod, upset and pointed at 
one end, may be driven to a depth of 
10 or 12 feet through most soils, 
and may be raised again by a handle, 
as shown in Fig. 3, which can if 
necessary be fastened to a lever, a 
stout wooden horse being used as a 
fulcrum. It is possible to reach 
still further by replacing the first 
heavy rod by a thinner and longer 
one driven in the same way. 


1 



Fig. 3.—Sounding-rod. 


When there are not many boulders or gravel-stones in the 
soil an iron pipe about 1 inch in diameter may be connected 
by hose with a fire-hydrant and sunk into the ground by the 
“jet process” to a considerable depth. By connecting the 
hose to the side of a T screwed to the end of the pipe and 
capping the top of this the pipe can in most cases be driven 
by hammer past any small stones or other hard obstacles. 

A modified post-hole auger can be used for the same pur¬ 
pose, with the advantage that by it samples of the soils passed 
through may be obtained. 


























I 10 


SE WEE A GE. 


The only certain method of detecting the presence of 
quicksand is by sinking a test-pit, though the absence of sand 
from the materials removed by other methods would of 
course be proof of its absence. The washings from a jet-pipe 
may be caught and from the sediment some idea be had of 
the materials encountered, though not of their consistency. 

The presence of ground-water in any quantity is fully as 
important a matter in designing as the presence of rock, and 
should be thoroughly investigated. Ground-water is fre¬ 
quently found in porous soils just at the base of a hill. It is 
usually found in gravelly soils, near hills or mountain 
streams whose waters percolate into the porous ground. 
Usually (although there are exceptions) but little water 
reaches the soil from rivers* whose beds are in most cases im¬ 
pervious. The presence and amount of ground-water can be 
known only through excavations, which should be made with 
that aim in view if none exist made previously for other pur¬ 
poses. In many cases a sufficient number of wells and cess¬ 
pools will have been dug to give a general idea of the depth 
and amount of ground-water to be encountered. 


CHAPTER VII. 


THE DESIGN. 

No general directions for designing a sewerage system can 
be given which will cover all the conditions met with in every 
case. But upon the principles stated may be based any 
special designs, care being taken to violate none of the 
requirements of sanitary sewerage. In many cases no emer¬ 
gency will arise out of the ordinary. To such the methods 
herein outlined apply, but even in the use of these skill and 
judgment must be employed, and it may frequently be neces¬ 
sary, as it is always desirable, to call upon the services of an 
experienced consulting engineer for a decision as to some of 
the vital principles involved in the design; such, for instance, 
as the system to be employed and the method of disposal. 
But many small cities and towns cannot afford this expense— 
or think they cannot—and the city engineer must rely wholly 
upon himself for the design as a whole and in detail. It is 
hoped that the principles already stated and the methods fol¬ 
lowing may be of service to him. 

Art. 32. General Principles. 

The first matter to be decided upon in preparing the design 
is, How much and what kind of sewage must be provided for? 
the second, What disposal shall be made of it? the third, 
What system—separate, combined, or compound—shall be 
employed ? 


hi 


112 


SEWERAGE. 


It is assumed that all urban districts require house-sewer¬ 
age. Local circumstances, financial, topographical, and geo¬ 
graphical, will usually decide whether or not storm-water also 
shall be removed by the sewers. In small cities there are 
usually a few places the removal of storm-water from which is 
almost imperative. These places must be ascertained, the 
area draining to them measured on the contour-map, and an 
estimate made of the run-off based upon the principles given 
in Articles 18-20. 

In towns or districts which are closely built up the storm¬ 
water should not flow in the gutters more than two blocks — 
or say 700 feet—before finding a sewer-inlet or some natural 
stream or channel into which it can discharge. In residence 
or suburban districts the same rule applies when the streets 
have impervious pavements and the yards are small. As the 
pavements become more pervious and the houses more scat¬ 
tered this distance can be considerably increased and the 
extent of the storm-sewer system proportionately reduced. 
The judgment as to how many localities (from a lack of water¬ 
courses or other reasons) need storm-sewers must be balanced 
against the funds available for such sewers. If possible, how¬ 
ever, the storm-sewers should serve as wide a territory as the 
house-sewerage system. 

In most small cities natural watercourses are retained to 
carry away the run-off, and the service rendered by these 
may be made adequate—if it is not already so—by enlarging, 
straightening, and walling them. (If the money necessary for 
substituting a storm-sewer for such a drain is available this 
should of course be done.) The residents along such a water¬ 
course should be prohibited from depositing any excreta, 
garbage, or other refuse therein; and if this is enforced and 
the stream so enlarged as to prevent overflowing it will 
become a good substitute for a storm-sewer, and much less 
objectionable than such small streams ordinarily are to the 


THE DESIGN. 


I 13 

occupants of the property it traverses. For the amount of 
water to be provided for from given areas see Arts. 17-19. 

A short summary of some of the principles previously 
stated may be given here to advantage, with applications of 
the same. 

The amount of house-sewage depends, first, upon the 
population to be provided for. This must be the population 
some years in the future; some say 30, some 50 years. The 
first seems preferable in most cases, since the larger sewers 
called for by the second will be less suited to the needs of the 
present, deposits dangerous to health more probable, and 
consequently cost of maintenance greater; also in most cases 
the difference in cost at compound interest for 30 years would 
amount to sufficient at the end of that time to build a system 
adequate for the increased needs. Moreover, the growth can¬ 
not be predicted with any great accuracy 30, and still less 50, 
years ahead. From the estimate of Baltimore’s growth made 
by the Sewerage Commission it is calculated that to pro¬ 
vide for a population for 30 years ahead would call for sewer- 
mains of twice the capacity at present required; while if that 
for 50 years ahead were adopted as the number to be provided 
for the mains would need to be more than three times such 
capacity. 

For making this prediction it is customary to plot all 
known past populations, each year and its corresponding 
population being made coordinates of as many points. A 
curve is passed as nearly through these points as possible, and 
with the same law of curvature is continued ahead far enough 
to cover the time required. It is evident that such a curve 
should not return on itself horizontally, but must approach 
an asymptote whose direction the judgment must decide; or 
the curve may in reality even reverse. This method is but a 
“ scientific guess,” but there seems to be no better one. As 
a general rule the smaller the city or town the greater the 


SEWERAGE. 


i 14 

probability of sudden and great unforeseen changes in the rate 
of growth. 

The estimate of per capita water-consumption is similarly 
difficult. There is no necessity for this exceeding 50 or 60 
gallons daily, and yet it may reach 200 or even 300 for any¬ 
thing which we know to the contrary. Since it can be con¬ 
fined well within the 100 mark by the use of meters and 
thorough inspection, it seems wasteful of capacity and capital 
to provide for more. The probability is that the near future 
will see the consumption almost universally reduced below 
this limit. 

The population decided upon times the per capita water- 
consumption and plus the leakage may be taken as the 
amount of sewage to be provided for. 

The character of the sewage, involving the proportionate 
amount of house-wastes and diluting-water, the character of 
the water supplied, the presence of acids or other manufac¬ 
turing wastes, will have a bearing upon the method of dis¬ 
posal. 

In deciding upon the disposal to be adopted, if that by 
dilution is practicable the laws of the State should be investi¬ 
gated to determine its legality; the direction and velocity of 
tides and currents should be known to be such as to remove 
the sewage continuously from rather than toward all shores 
or other places where it may be deposited and create a 
nuisance; the number of gallons of unpolluted water passing 
the outlet each day should be equivalent to at least 1500 
times the population; the velocity of the water past the out¬ 
let must be sufficient to prevent the deposit of sewage matter 
at or near said outlet. The effect of the discharge upon 
bathing-beaches, upon fish, oysters, or other food matter, 
upon the water-supply of towns below, or upon manufactur¬ 
ing interests—these must all be studied, both on their scien¬ 
tific and commercial sides. 


THE DESIGN . 


115 

If from these investigations dilution is found inadvisable 
the method of treatment best adapted to the circumstances 
must be sought. Search should be made for a spot or 
spots which are low and flat, but not boggy, whose soil is 
pervious and whose value is low (although land which pos¬ 
sesses none of these qualities can be used for sewage disposal), 
and whose extent is sufficient for years to come. If the 
sewage must be thoroughly purified filtration or irrigation 
must be used, alone or in connection with precipitation or 
septic tanks. Chemical precipitation may be employed alone 
where a removal of 50$ to 65$ of the impurities will be suffi¬ 
cient. (See Chapters II, XVI, XVII, and XVIII for a dis¬ 
cussion of this subject, which should be carefully studied 
before deciding upon any scheme of treatment.) 

It will usually be well to make preliminary plans based 
upon each of two or three methods of disposal and compare 
them from both sanitary and financial points of view. 

A decision as to the system to be employed should ordi¬ 
narily rest largely upon the decisions of the two previous 
points. If treatment of the sewage is necessary or will 
probably become so in the course of 20 or 30 years, or if the 
house-sewage is to be discharged at some distance from the 
centre of the city, the separate or compound system will 
usually be advisable. 

If there are a number of convenient points along a water 
front at each of which house-sewage can be discharged with¬ 
out nuisance the combined system may be the cheapest and 
most desirable. If there already exist large sewers discharg¬ 
ing at various points where the discharge of house-sewage 
creates a nuisance, or of a character not adapted to carrying 
house-sewage (because of flat bottoms or rough interior), the 
separate system will usually be advisable, the old sewers 
being used in the storm-sewer system. If such large sewers 
are adapted in interior surface and form to carrying house- 


116 


SE WEE A GE. 


sewage, however, they may be retained for this purpose, but 
an intercepting sewer built to receive from them the dry- 
weather flow and convey it to a suitable outlet, the storm¬ 
water discharging through the previous outlets. 

In all these matters, however, engineering experience and 
judgment, and not fixed rules, should be the basis of decision. 

The general rule in sewerage, as in other engineering work, 
is: obtain the best results and at the least cost. Certainty 
of attaining this will frequently require the preparation and 
comparison of alternative plans, both of the system as a 
whole and of its separate parts. 

Art. 33. Subdivision into Districts. 

For the purpose of sewerage-designing the territory under 
consideration is ordinarily divided into two sets of districts, 
one based upon the density of population, the other upon the 
slope of the ground-surface. 

The former division should take as a basis the probable 
density of population per acre of different sections at some 
time—say 30 years—in the future, since the system must 
serve the population at that time as well as in the present. 
It will be convenient to base the division upon population per 
acre of 20, 30, and other factors of 10, 20 being the minimum 
assumed for habitable districts in most cities. The maximum 
may run up to 150 or more per acre. As this division is for 
the purpose of design only and is not usually shown upon the 
finished map, it may be designated by bounding-lines or by 
tints upon a working map. (It will be well to have several 
copies—white or blue prints will do—of the city map as work¬ 
ing maps.) Having made the above subdivision, the total 
population of each area, calculated from the assumed density 
of population, should be ascertained, and the sum of all these 
compared with the future total population as estimated by use 


THE DESIGN. 


II 7 


of the curve (Art. 32). It may exceed this by a small 
amount—say 10^—to allow for incorrect apportioning of 
densities. If it does not at least equal it changes in the 
extent of the different areas should be made sufficient to give 
this total and at such points as the engineer’s best judgment 
dictates. 

The second subdivision is that into drainage districts. 
For this purpose a carefully prepared contour-map of the city 
or area to be sewered is necessary. Each district is to con¬ 
tain all the territory draining into one main sewer, together 
with that main down to its outlet or junction with the inter¬ 
cepting or outlet sewer. Under some plans of sewer assess¬ 
ments this subdivision is necessary for other than engineering 
purposes. For house-sewers it can usually be best made 
after the designing of the sewers is completed. For storm- 
sewers, however, it should be made after the lines are located, 
but before the sizes are determined upon, to facilitate calcu¬ 
lation of the latter. 

Art. 34. Locating the Sewer-lines. 

Unless this location is already occupied by gas- or water- 
pipes or a street-railroad, house and combined sewers are in 
most cases located in the centres of streets or alleys, the cost 
to the householders on each side for house-connections being 
thus made equal. In some cities the sewers are located under 
the sidewalks, there being a line on each side of the street. 
This plan, which is used at Washington, D. C., quite exten¬ 
sively, is usually adopted in the case of wide streets, since 
there the cost of the extra line is less than that of the addi¬ 
tional lengths of house-connections required by a single sewer. 
From a financial standpoint the double line is cheaper when 
the cost of a minimum-sized sewer (6- or 8-inch) of a length 
equal to the average house-lot frontage is less than the cost 


118 


SE WEE A GE. 


of a house-connection of a length equal to the distance 
between the two sewer-lines. Another advantage of side 
sewers is that the street-paving need not be torn up in making 
house-connections. A serious disadvantage is that the dis¬ 
tance from the upper end of each line to the point where the 
sewage flow is self-cleansing in volume and velocity will be 
double that when but a single line is laid. Also the roots of 
shade-trees are apt to cause serious trouble by entering the 
pipe-joints. Probably the best method of avoiding both 
these last objections and that of the continual tearing up of 
the street-pavement is to lay the sewer in the street centre 
and at the same time carry each house-connection to the curb. 

Where a city has alleys intermediate between the streets 
it may sometimes be advisable to carry the sewers through 
these rather than through the streets, the principal argument 
for this being that less valuable paving is destroyed and less 
obstruction caused to traffic by the work of construction. 
On the other hand the house-connection will be longer, and 
both the cost increased and the grade in such connection 
decreased, if the distance from the house to the street centre 
is less than that to the alley centre, as is generally the case. 
Moreover, the paving in an alley should be equally as good as 
that in a street, and the unevenness consequent on sewer 
construction is exceedingly apt to contribute to the disease¬ 
breeding slovenliness in what is often at its best an 
elongated Gehenna. Again, . in a narrow alley the space 
available for piling the excavated dirt is so contracted that the 
cost of construction is frequently increased by a very appre¬ 
ciable amount on this account. On a side hill, however, it 
may often be advisable or even necessary to locate sewers in 
the alleys for the drainage of houses on the lower sides of 
streets above. 

Sewers should be laid in continuous straight lines, as far 
as possible. 


THE DESIGN . 


HQ 

No turn greater than a right angle should be made at any 
one point by any sewer less than 24 inches in diameter, and 
any turn whatever made by such a sewer should be in a man¬ 
hole, by means of a curved channel. For sewers larger than 
12 or 15 inches it is advisable to use two manholes in making 



Fig. 4.—Alignment of Sewer-junctions. 


a bend greater than 45 0 (see Fig. 4). Brick sewers more 
than 24 inches in diameter may be laid on curves, since they 
can be entered for inspection or cleaning. 

Each lateral sewer should take the most direct course to 
its main, each main the most direct course to its outlet, and 
the number of mains should be as few as possible. This 
serves both economy and sanitary efficiency. 

The dead ends should be made as few as possible, even at 
some expense of additional excavation, but not by reducing 
mean velocities below 2.5 feet per second; nor is it ordinarily 
serviceable to unite the upper ends of sewers flowing in oppo¬ 
site directions. 

House-sewers should be carried within reach, as regards 
both horizontal distance and grade, of every lot in the 
sewered district. 

Storm-sewers should have as few branches as can be 














120 


SE WEE A GE. 


made to reach all the street-inlets, to better insure which such 
inlets should be located previous to the location of the sewer¬ 
lines. 

It is generally advisable to avoid crossing private property 
where possible, since legal complications and delays might 
result from such crossing. This will frequently be impossible, 
however, particularly near outlets. 

The sewer-lines can usually be laid out directly upon a 
contoured working map, an approximate rough estimate of 
the necessary size and consequent minimum slope of each 
sewer being made, that deep or shallow cutting may be 
avoided. The direction of flow should be indicated by 
arrows. 

In the separate system the storm-water sewers should 
usually be placed on one side of the street centres, the house- 
sewers being placed in the centres. The two should never be 
placed one above the other in the same trench unless in con¬ 
tact with each other or connected by masonry. 


Art. 35. Volume of House-sewage. 


Since the grade of a sewer is limited by its size, and the 
size is determined by the grade and consequent velocity, but 
to even a greater extent by the maximum volume of sewage 


to be carried, this last must be determined before either the 
limiting grade or size can be decided upon. If the maximum 
rate of water-consumption be taken at 175 gallons per day 
per capita the maximum volume per second to be carried by 
/• , . , v . 175 DA 

a sewer (in cubic feet) is — g ^ S6400 ’ in which D = density 

of population and A = the area in acres. 

Beginning at the summit of each lateral, it is clear that it 
is unnecessary to calculate the capacity required for any sec¬ 
tion of sewer until the point is reached where the volume of 



THE DESIGN. 


121 


sewage to be carried exceeds the capacity of the smallest 
sewer used at the given grade. For an 8-inch pipe flowing 
half full with an average velocity of 2.5 feet per second this 

'3.1416 X 16 X 2.5 


volume is about 


= jo.4363 cubic feet 


2 X 144 

per second, which would be contributed as a maximum flow 

'0.4363 X 7-48 X 86400 


by a population of 


175 


= J1611, or 


about 40 acres having a density of population of 40. 

At the point where the sewage from the tributary popula¬ 
tion exceeds the capacity of the sewer its size must be 
enlarged to the next market size of pipe or the next size of 
brick sewer convenient for construction. 

The allowance for leakage into the sewer of ground-water, 
which should be a small proportion of the sewage proper, may 
be added at intervals, according to the engineer’s judgment, 
based on such data as he is able to obtain. 

In calculating these volumes it is advisable to begin with 
the furthermost lateral sewer first; where this joins another 
the contributions of both are to be added to determine the 
flow below that point, and in tracing down this line as each 
branch is encountered its contribution must be calculated and 
added. Decision having been made, after a study of the 
topographical map, as to the line of sewer into which each 
section of undeveloped territory will drain when sewered, the 
sewage which this area will ultimately contribute should be 
placed at the heads of the volumes of flow in this line. 

An excellent method of making these calculations is 
shown on page 122. The sewerage-map Plate No. Ill was 
used for this table. 

In this case it is seen that the capacity of an 8-inch pipe 
at the minimum grade was reached at the junction of the 
Newcastle and Budd Street sewers, but the line down Budd 
has 1 : 50 as its grade, and no increase of size is yet necessary. 





122 


SE WERA GE. 


CALCULATION OF SEWAGE QUANTITIES AND SEWER SIZES. 


Street. 

From 

To 

Area. 

Acres. 

Density. 

Popula¬ 

tion- 

Sewage. 

Gallons 

per Day. 

Total 

Sewage. 

Grade. 

Size. J 

Prospect 

Newcastle 

Walnut 

IO .4 

20 

208 

36400 


j i : 30 

1 1 : 11 

8 in. 

fc« 

Walnut 

Prindle 

Prospect 

i -7 

20 

34 

5950 


1 : 20 

(4 

Walnut 

Prospect 

Liberty 

1.9 

20 

38 

6750 


1 : 20 

44 

Liberty (extended) 

Newcastle 

Walnut 

12. 7 

20 

254 

AAA 



4 4 

Walnut 

Liberty 

Budd 

8.2 

20 

164 

28700 

122250 

1 : 300 

44 

Newcastle 

Prospect 

Liberty 

1 ’5 

20 

3 ° 

5250 


1 : 300 

44 

Undeveloped terri 

tory tributa 

ry to Newcastle 

27 • 2 

20 


0 5 550 




Newcastle 

Liberty 

Budd 

7-5 

20 

150 

26250 


1 : 300 

8 in. 

Undeveloped terri 

tory tributa 

ry to Budd 

44.0 

20 

880 

154000 

281050 



Budd 

Newcastle 

Walnut 

II.O 

20 

220 

38500 

3 i 95 So 

1 : 50 

8 in. 

Budd 

Walnut 

River 


20 

60 

10500 

452300 


10 “ 

Budd 

Walnut 

River 

Ground-water 






At the junction of Budd and Walnut the sewage amounts to 
441,800 gallons, or 40.9 cubic feet per minute, and the sewer 
from there to the river must have the minimum grade allow¬ 
able. The size must therefore be increased, and as the next 
market size, 10-inch, has a capacity at that grade when two 
thirds full of about 590,000 gallons, it is therefore sufficiently 
large for the rest of the line, including sewage contributed 
along its length and ground-water. No ground-water was 
anticipated on the hill side, but it was considered probable 
that on Budd below Walnut this would leak into the sewer at 
the rate of two gallons per day per foot of sewer (see Art. 
46). 


Art. 36. Volume of Storm-sewage. 

The principles stated in Articles 16-20 will be used as a 
basis in determining the amount of storm-water to be pro¬ 
vided for. Decision should first be made as to whether this 
shall include run-off from storms of the first, second, or third 
class. Then the past rates of fall of such storms should be 
ascertained. If the records of such rates extending over a 
series of years are not obtainable use may be made of the 
rainfall data given in Art. 17. Plate No. IV shows rainfall- 
curves for average maximum rains of the second class, from 








































THE DESIGN . 


123 


Plate III. 















































































124 


SE WEE A GE. 


which may be taken the amount of rain to be expected during 

% 

any given period of time in the localities named. If sufficient 
rainfall data for the place in question are available a similar 
curve for that place plotted from these data will be found 
serviceable. If these data have not been kept by the city it 
is probable that the rates for a neighboring city can be 
obtained from the Weather Bureau at Washington, which now 
has self-registering gauges in over fifty cities of the United 
States. 

Next to be determined is the character of surface of the 
streets and included areas in each section drained; that is, the 
amount of impervious surface. The safest course would be 
to assume that every street-surface is, or will be made, wholly 
impervious; that the space covered by each building will also 
be impervious; and that in residence districts the remaining 
areas will be 30$ to 80# impervious at the time of heavy 
downpours, since rainfall records show that at least 25^ of 
these are preceded by one or more hours of rainfall, which 
increase the natural imperviousness. These figures will be 
used in illustrative calculations in this work; but the judgment 
of the engineer, based on local conditions, may well dictate 
others, differing for each case considered. For instance, a 
closely built-up business district having paved yards and 
courts may be assumed as all wholly impervious. 

These points having been decided, the inlets should be 
located on a contour-map. Also it will be well to state in 
figures on each city block its area and percentage of imper¬ 
viousness (see Plate V). 

The percentage of imperviousness may be calculated thus: 

Let / = the average length of a city block- 
b= “ “ breadth “ “ 

number of front feet to a building- 


f = 


u 


«( 


d = 


i « 


< < 


lot; 

depth of a building-lot; 


RATE OF RAINFALL IN INCHES PER HOUR, OR CUBIC FEET PER SECOND PER ACRE. 


THE DESIGN. 


125 


Plate IV. DURATION OF RAIN IN MINUTES. 



LENGTH OF AREA IN FEET. 


































































































































































































































































































































































































































































































































126 


SEIVERA GE. 


a — the average area covered by a building; 
w = “ “ width of street; 

i= “ “ percentage of imperviousness of yards, 

courts, etc., expressed as a decimal; 
/= “ percentage of imperviousness of the entire 
area, expressed as a decimal. 

Then 

w{l+b + w)+ i(lb - 

I ~ lb -f- w(l -)- b + w) 

lb(a + ifd — id) -f- wfd(l -f- b + w) 
= fd\lb + w(l + b + w)\ * 

As an example, let / = 450, b — 2 50, / = 5°, d — 125 , 
a = 1200 sq. ft., w = 66, i — .60; then I — .777, or say .78. 

When most of the above factors must be estimated by 
judgment only, as for areas not yet opened up or fully devel¬ 
oped, it may be as well to estimate / at once. 

By comparing this formula with that on page 36 we see 
that 

lb{a -f- ifd — id) -j- wfd{l -f- b -f- w) 

~ 43560 Ibo * 

which formula can be used when P has already been calcu¬ 
lated. The relation between I and P will, it is evident, vary 
in different cities and also in different parts of the same city. 

The map having been thus prepared, with the a and / on 
each block, the uppermost corner of the drainage-area furthest 
from the outlet may be taken as a starting-point. If there 
are beyond this any areas not included in the sewered districts, 
but the run-off from which flows into such districts, this run¬ 
off must be estimated and provided for. For this purpose the 
formula Q = AIR may be used, A being the total area, I the 
coefficient of imperviousness, and R the maximum rate of 
rainfall (of the class to be provided for) for that length of 





THE DESIGN. 


127 


time which will elapse while the run-off from the furthest 
point of the drainage-area is reaching the sewer. This time 
is an uncertain quantity and will to a certain extent vary 
with R. Some engineers assume a velocity of about 2 feet 
per second over the surface. The formula v — 1000/ VS is 
offered as an empirical one for calculating the velocity of 
run-off over the surface in feet per minute, 5 being the sine 
of the slope. While / does not directly affect this velocity, 
it is observed that the most impervious surfaces usually offer 
the least obstruction to the flow of water, and vice versa . 
The time t for which r is assumed is obtained by dividing 
v into /, the length of the furthest corner of the drainage-area 
from the sewer. 

The same method is also applied to determining the time 
of run-off from each smaller area to its inlet, / in such cases 
being taken as the distance by gutter of the furthest point 
from its inlet. 

The amount of run-off to each point of interception thus 
found must be provided for by inlets of sufficient size and 
number (see Art. 41) and by ample sewer capacity. The fol¬ 
lowing tabulation of a calculation by the above method for 
the district shown in Plate V is given as an illustration, a is 
the size of each sub-area, I its imperviousness; AI is in each 
case the sum of all the preceding al's. s is the surface-slope 
of the sub-area, l is the greatest distance traversed by the 
run-off in crossing each sub-area, t is the time occupied by 
the run-off in travelling the distance /, r is the rate of rainfall 
for the time /, q = air . 5 is the slope of the sewer removing 

the run-off from the point in question, L its length to the 
point next considered (usually the next inlet or sewer-junc¬ 
tion), 7Ms the time occupied by the run-off in flowing from 
the extreme limit of the entire drainage-area A over the sur¬ 
face and through the sewers to the point under consideration, 
R is the rate of rainfall for the time T, Q is the total 


AVENUE 


128 


SEWERAGE . 


Plate V, 


4TH 


o 

3 

sS 

u o 

5 5 

a z 1 Q 

5 < t “ 

2 S * * 

O > toio 
» g I COO 
a. t a. 
g a co 

< OC 


1 ST 5 1“ j! N CQ 


STREET 



STREET 


a 


DIRECTION 

INLET 

MANHOLE 


OF FLOW OF RUN-OFF 
































































* r and R taken from the rainfall-curve (Plate IV, page 125) for the New England States. 


THE DESIGN. I2Q 











C 

! 










3 











CL 











O 

r 










< 

0 









2 

a 

0 

O 

P 

rt 









O 

-0 

0 

0 

O' 

00 

v\ 

•vl 

43 * 

03 

to 

M 

t* 

CL 

D 

O 


s 









t-S 

0 

3 

0 

3 








r-t 

O 

> 

•-1 

CD 

O 









p 

3 * 

3 * 








r-t 


P 

P 








0 



►— * 










*“*■% 









0; 


V ' 

'- * 










M 

M 

03 

03 

03 

03 

to 

to 

to 

4^ 

0 

& 

00 

00 

O' 

O' 

O' 

O' 

cn 

cn 

cn 



CO 

00 

00 

co 

00 

CO 

00 

CO 

00 

O' 

k, 

0 

0 

0 

O 

0 

0 

0 

0 

0 

0 











to 


W 

M 

to 

to 

to 

to 

to 

to 

to 

4 * 

& 

■P 

4 - 

CO 

00 

CO 

00 

b 

b 

b 


s 

4 * 

4 * 

co 

00 

00 

00 






4 - 

-O 

-0 


CO 

03 

03 

to 

to 

to 


4 * 

to 

M 

CO 

cn 

to 

O 

00 

O' 

4 ^ 


4 ^ 

0 

cn 

O' 


OO 





s 

O 

O' 

to 

4 * 

O' 

CO 






O 

b 

b 

b 

b 

b 

b 

b 

b 

O 


O 

0 

0 

0 

0 

HH 

M 

M 

M 

cn 


"-X 

C J\ 

^x 

cn 


CO 















03 


O' 

O' 

CO 

CO 

00 

00 

O' 

O' 

O' 

O' 


03 

CO 

0 

0 

03 

03 

to 

M 

to 

0 


O 

0 

0 

0 

O 

0 

cn 

cn 

cn 

0 



M 

M 

M 

HH 





to 


O 

M 

M 

-0 

to 

0 


•0 

^x 

O' 

t* 

• 

• 

• 

• 

• 

• 


• 

• 

• 


4 - 

M 

0 

M 

4 > 

M 

00 


co 

0 


to 

to 

to 

to 

to 

to 

CO 

03 

03 

W 









• 


0 


O' 

-P 

O' 

vb 

M 

M 

M 

-4 

* 










43. 


-0 

03 


O' 

^x 

00 

O' 

O' 

O' 

O 


to 

O 

cn 

vO 

cn 

4 k 

to 

to 

to 

00 

K 3 

, 





• 

• 


• 

• 


0 

0 





0 

0 

O 

O 


8 

8 

Co 

4 * 





00 

cn 


O' 

0 


to 





M 

to 


to 

to 


0 





to 

co 


^x 

0 

■s 

O' 





4 * 

•O 


»4 

0 







to 

M 

• 


M 

M 

1 * 

c> 





O' 




Vj 


-4 





W 

cn 


-0 

43 . 


M 





cn 

• 

M 


4- 

0 

fO 

O 





0 

b 


to 

00 


4 * 

00 





to 

to 

4 > 


03 

0 

03 

O 

Size of Sewer. 

>* 





>» 

- 


- 

- 


4^ 

03 

to 





-O 

M 

0 

4 * 

to 

4 * 


4 k 

03 

O' 

4 ^ 

03 

to 

Velocity of Flow. 

Feet per Minute. 






co 

cn 


03 

03 







03 

M 


M 

O 

h* 






O 

O 


O 

O 


03 

CL 





03 

CL 

> 

< 


to 

CL 

> 

< 


cn 





in 

n» 


cn 



rt 





r-t 

• 



r-t 


r 

>* 





«# 

0 


- 

w 

0 

> 





> 



> 


p 

< 





< 

to 


<* 

M 


n 

• 





n 

CL 


a 

C/J 

r-t 

O 

P 

o 





Cd 

cn 

r-t 


cd 

cn - 

r-t 

O 

t-H 

r+ 





r+ 




• 

in 

0 





0 

rt 


0 

rt 

a 

> 

< 

0 





> 

<* 

ft 

0 

03 

CL 


> 

<5 

o 

0 

to 

CL 

n 

n 

O 





O* 

cn 

r-t 


0 

C/) 

ft 


• 








• 

• 

























































SE WEE A GE. 


130 

amount of run-off from all the drainage-areas above = AIR. 
q(= air) as well as Q should be calculated for each sub-area, 
and if the Q for any stretch of sewer is at any place less than 
the q immediately tributary to the same the latter should 
determine the size. 

Plate IV will be found convenient for determining a , and 
also R when the rates of rainfall of the place in question can 
be represented by any of the curves there given, these being 
for rains of the second class. To find a in acres from the 
diagram, use one dimension (in feet) of the area (or of an 
equivalent rectangle if it is not rectangular) as an ordinate 
and find the corresponding abscissa of the acre-curve in the 
diagram; divide this into the other dimension of the area and 
the quotient will be a in acres. 

By the table the run-off from the undeveloped territory is 
placed at 40.8 cubic feet per second, which is carried by a 
36-inch sewer on a .6# grade for 360 feet, where it receives 
still more sewage; the maximum amount to be received there, 
both over the surface and through the sewer, being 44.2 cubic 
feet, although q for the block No. 1 alone is 6.2 cubic feet. 
But Q is not equal to 40.8 -(- 6.2, because the latter quantity 
was due to a rainfall of 6.25 minutes’ duration, or rather to 
the maximum rate for that time, during which only such 
water would have arrived from the upper end of the drainage- 
area as was due to a lower rate of rainfall; but the time of 
27.7 minutes is that for which the run-off is calculated from 
both the undeveloped territory and block No. 1. Blocks 
No. 2 and No. 3 both reach the sewer at the same point, and, 
taking the rate of rainfall for 28.4 minutes, we have a total 
run-off from all the territory above of 51.0 cubic feet per 
second and, the grade being .5#, a 42-inch sewer is found to 
be necessary. 

Blocks No. 4 and No. 7 discharge first into a branch 
sewer, which it is found should be 22 inches in diameter. 


THE DESIGN. 


131 

Where this joins the main the run-off from blocks No. 5 and 
No. 8 and from half of No. 6 and No. 9 also reaches it, and it 
must consequently be increased in size. The time T at this 
point is 26.09-j- (in the Ave. B sewer) -f- 0.7 (in the Second 
Street sewer)-j- 1.2 (in the Ave. C sewer), or 29.6 minutes, 
and the rate of rainfall for this time is used for the run-off 
from the entire area. 

It will be seen that the method here employed is but a 
practical application of the principles stated in Art. 18. 
More, and more accurate, data for determining t and /, as 
well as R y are needed before this or any method can be relied 
upon to give more than general approximations to the run-off. 
Fortunately with the method here given the approximation 
becomes more close as the area becomes more urban, and is 
most so in the most densely populated districts, where the 
danger from gorged sewers would be greatest. 

Art. 37. Grade, Size, and Depth of Sewers. 

For both determining and recording the grades of the 
proposed sewers use is usually made of the profiles of the 
streets, plotted from the level notes. Upon these a vertical 
longitudinal section of the proposed sewer through its centre 
line is placed, thus showing the size, grade, and depth of the 
sewer. While designing, however, it will be found convenient 
to pencil in the line of the invert only, since then changes in 
its vertical location can more readily be made. 

A short experience in sewer-designing will demonstrate 
how mutually involved are Q , 5 , the diameter and the depth 
of the sewer. In many cases it will be necessary to alter and 
realter the grade and diameter before obtaining for each reach 
of sewer the best obtainable depth and velocity. Q is a fixed 
quantity for any given case, N may vary between fixed limits, 
the size also has its limits in some cases, but the depth of the 


i3 2 


SEIVEE A GE. 


sewer may vary from any distance below to any distance above 
ground. A depth of 25 or 30 feet is obtained in many 
sewerage systems, and even 50 feet or more has been reached 
in open cut, while sewers have been laid in tunnel at still 
greater depths. Where possible deep sewers should run 
through wide streets, that the danger to building-foundations 
may be kept as small as possible; and they should avoid the 
busiest thoroughfares unless these are also the widest streets 
and the soil is treacherous. The sewer may in some cases be 
carried on bridges or trestles, as in crossing a stream or ground 
lower than the hydraulic gradient. In many such locations, 
however, this position will be impossible, owing to traffic on 
the river, to danger from floods, to blocking of streets, or to 
prohibitive cost of construction. In such cases the pipe may 
be placed under the surface of the ground or in the bed of 
the stream, being thus below the hydraulic gradient. Such a 
downward loop is called an inverted siphon. Many instances 
of these are in use, and if care be taken in their design and 
construction they need give no trouble. It will not be possi¬ 
ble, or at least advisable, to connect any buildings to an 
inverted siphon, since the sewage will continually stand in 
the connections up to the level of the hydraulic gradient of 
the siphon. 

The depth of storm-sewers is usually fixed by grade 
requirements only; the covering over them, however, should 
be not less than two feet and would better be three or four 
feet. The minimum depth to which house or combined 
sewers should be laid will usually be decided by local circum¬ 
stances or customs. It is generally desirable to lay them 
somewhat deeper than the gas- or water-pipes, that these may 
not interfere with them. The city of Brooklyn some years 
ago fixed 12 feet as the depth to which all (combined) sewers 
are to be laid, unless the maintenance of proper velocity 
requires a less or greater one. In Philadelphia 14 feet is the 


THE DESIGN. 


133 


standard depth, in Washington, D. C., 10 feet. In residence 
districts in the smaller cities 7 to 10 feet is usually sufficient, 
although in a street running along a hillside a much greater 
depth may be called for by the depth of basements upon the 
lower side of the street. In streets which are already built 
up the sewer should be deep enough to drain all basements 
and cellars, with the exception, perhaps, of an occasional one 
of unusual depth. To insure this the cellar depths taken 
during the survey should be indicated in their proper positions 
upon the profiles of their respective streets. In many 
Southern cities where there are no cellars under the dwellings 
and there is little danger of frost the sewers may be given a 
depth of covering of only 3 or 4 feet. In the North 6 feet is 
probably the least depth which should be given to the flow¬ 
line save under exceptional circumstances. The maximum 
depth should be kept at 14 to 16 feet if possible, since below 
this the cost rapidly increases. When the depth is consider¬ 
able the expense of making house-connections may become 
excessive. It may in such cases be found cheaper to lay a 
small sewer about 7 or 8 feet below the surface and following 
the surface grade, which may be with or against the grade of 
the deep sewer, to a manhole in the deep sewer into which 
this shallow one can discharge. 

Before fixing the grade it is well to prepare tables similar 
to those given in Articles 35 and 36, and also to calculate as 
closely as possible the total amount of sewage reaching each 
outlet. 

Very often the main sewer for a long distance from the 
outlet must be laid at a minimum grade if pumping is to be 
avoided or the lift kept as small as possible. In such a case 
the grade of this main will be the first to be located upon the 
profile, the outlet being placed as low as is permissible. This 
should never be below ordinary high water unless absolutely 
necessary, and under no consideration should it be below or 


134 


SEIVEEA GE. 


even as low as ordinary low water; or rather this should be 
true for the hydraulic gradient, although the last few feet of 
the sewer may be given a steeper grade to bring the outlet 
below the water-surface or into the channel. 

There may be other lines also where the surface elevations 
demand the flattest possible grades; that is, the grades which 
will give the minimum permissible velocity. This grade will 
depend upon the size of the sewer, and this again upon 
the quantity of sewage. To ascertain this size, reduce the 
maximum sewage flow to cubic feet per second, divide by the 
desired velocity of flow in feet per second, multiply the 
quotient by 1.5 for mains or 2 for laterals, and find the diam¬ 
eter of a circle having this product as its area, which will be 
the sewer diameter required. Or, divide the gallons of 
sewage per day times 1.5 or 2, as the case may be, by the 
required velocity in feet per second, and take the size corre¬ 
sponding to the next highest quantity in the following table: 

Table No. 16 . 

Size of sewer.... 8" 10" 12" 15" 

Gallons of sewage per day. 225,500 352,500 507,600 792,800 

v 

Size of sewer. ..,. 18" 20" 24" 

Gallons of sewage per day . 1,141,700 1,410,300 2,030,500 

v 

Where possible the grades of house-sewers should be such 
as to give a velocity of from 3 to 4 feet per second, and those 
of storm-sewers from 4 to 5 feet per second. The demands 
of economical construction and the necessity for sufficient fall 
in house-connections should not, however, be sacrificed to 
reduce velocities to less than 10 or 12 feet, which, however, 
should be the maximum allowed. 

If it is possible the grade of the various sewers should be 
so proportioned that the velocity of the sewage shall increase 
as the outlet is approached, or at least it should not decrease, 








THE DESIGN. 


135 


since a decrease in velocity may cause a deposit of suspended 
matter. Frequently, however, it is impossible to attain this 
in the design, since the flattest surface slopes are usually 
nearest to the outlet and the sewer grades are largely con¬ 
trolled by these. 

From the formulas Q — aV and V — c VRS, considering 
the sewer as flowing full, and giving c a constant value of 85, 
which will in no case vary more than 10 % from Kutter’s c for 
pipes ranging from 8 to 18 inches diameter, we have the 
formula 

c K S '*0 

V 5 = —^ - .o 79 6c'S'Q, 

4 7 t 

or 

V=2i.i VSTQ* 


V being in feet and Q in cubic feet per second. This formula 
should not be used where any considerable accuracy is 
demanded, but will be found convenient for use in fixing the 
first approximate grades. If V is to be a constant S must vary 
inversely as VQ. 


f 


S , however, equals y if f equals the fall of the grade for 


a length /. If /, l", etc., be taken as the lengths between 

successive manholes, /, f", etc., as the corresponding 

falls, and Q> Q\ Q", etc., as the quantities of sewage flowing 
through these lengths, then 



/ 


// 


in 


VQ ", etc.; 


a l so y_[_ f f _j- f" -j- etc. = F , the total fall from the head to 
the outlet of the system. Knowing F, and / and Q for each 
length between manholes, we can obtain the values of /, /', 
f " 9 etc. As just stated, it is seldom that an entire system 
can be designed to give a constant velocity to the sewage, 





SEWERAGE. 


136 

but this is sometimes possible in separate drainage-areas, a 
constant velocity being obtained in each area. 

Still more important than obtaining a constant or con¬ 
stantly increasing velocity is the keeping of the velocity within 
the limits given in Art. 22. If the ground-surface is too flat 
to permit of obtaining this velocity by gravity pumping must 
be resorted to (see Art. 42). If the surface is steeper than is 
permissible for the sewer the sewer grades can be broken and 
a drop made at each manhole (see Art. 41). 

A slight drop in the grade should be made at each man¬ 
hole on flat grades to compensate for the obstruction offered 
by curves, etc., at this point, and for slight errors in measure¬ 
ment. 0.02 or 0.03 feet is usually sufficient. 

Of the above principles the most important is that the 
velocity of the sewage shall be within the proper limits; then 
that all basements and cellars to a reasonable depth shall be 
drained by house-sewers; also the depth of excavation should 
be kept as light as possible, and the principles outlined in 
Art. 34 should be regarded. The obtaining of the nearest 
possible approach to an ideal design will usually require many 
changes in, and rearrangement of, both lines and grades, since 
a change in those of one lateral may in some way affect the 
entire system. 

The preliminary grades having been thus fixed according 
to the desirable depths and velocities of flow, the size of the 
sewer for each reach should be calculated or taken from the 
diagram and the velocities checked by accurate calculation. 
Additional changes, usually slight, will probably be required 
to obtain the best values for each interdependent velocity, 
size, and depth. The junctions and crossings of the sewer-lines 
must be carefully examined and adapted to each other. It is 
a good plan to make a list of all the manholes, showing for 
each the elevation at which each sewer enters and leaves it. 
Two sewer-lines should never intersect each other, each 


THE DESIGN. 


137 


having a continuous grade; either one should discharge from 
both directions into the other or they should cross, the one 
above the other. 

At junctions the surface of the sewage in the contributing 
sewer should never be designed to be lower than that in the 
other; that is, if they are both branch sewers the centre of 
the tributary should not be below the centre of the intercept¬ 
ing sewer; if the larger is a main the centre of the smaller 
should not be lower than a point two thirds the diameter of 
the larger above its invert. It would be still better to place 
the invert of the tributary above the sewage-surface in the 
interceptor, particularly when the former drains but a small 
district; but where the total fall possible is slight none of it 
need be utilized for this purpose. 

Difficulty will sometimes be found in so arranging the 
comparative depths of storm- and house-sewers that the 
house-connections can pass under or over the former. In 
some cases this may be impossible, and it may be necessary 
to place a house-sewer on each side of the storm-sewer. 

Reference to the data of locations and depths of gas- and 
water-pipes and other existing sub-surface systems should be 
constantly made and the sewers so designed as to interfere 
with them as little as possible. 

On the profile of each sewer-line the elevation of all trans¬ 
verse sewers should be indicated and a cross-section of the 
sewer shown. On the finished profile it is well to indicate 
the thickness and material of the sewer-walls and of all man¬ 
holes, lamp-holes, and other appurtenances. The materials 
may be indicated by colors, as red for brick, brown for sewer- 
pipe, etc. The grade, length, and size of the sewer between 
each two manholes should be given in figures, as well as the 
exact elevation of the invert at each change of grade. 


1 


138 


SE WEE A GE. 


Art. 38. Inverted Siphons. 

Since the ordinary sewer is designed to flow only J to f 
full, while an inverted siphon, being under a head, will flow 
full bore, the velocity in the latter will be only i to § that in 
the sewer laid to the hydraulic gradient, if they are of the 
same size. On account of the difficulty of access and repairs 
it is especially necessary that the velocity of flow in the siphon 
should be at least as great as that in the ordinary sewer, that 
deposits may be prevented. This can be attained only by 
reducing the size of the siphon-pipe. Moreover, this velocity 
should be had from the beginning of the use of the system; 
and therefore this size should be designed to give sufficient 
velocity to the sewage from the first. This first sewage flow 
may be doubled or trebled as time passes, and the increase 
may then be provided for either by giving sufficient fall to the 
siphon originally to produce the greater velocity necessary or 
by additional siphon-pipes. Usually at least two siphon- 
pipes are laid at the first, that while one is being emptied 
and cleaned the other may be used. The friction-head in the 
inverted siphon will be greater than if the sewer were laid to 
the hydraulic gradient, and consequently the gradient must 
be steeper. The difference in elevation of the two ends of 
the siphon should be equal to the fall required by a sewer of 
the same size flowing full and of the length of the entire 
siphon (which is not the horizontal distance between its ends) 
to pass the given amount of sewage. 

The velocity of flow in an inverted siphon is entirely inde¬ 
pendent of the fall therein, but depends upon the quantity 
of sewage, since all of this must, but no more can, pass 
through it. If the fall in the inverted siphon is not sufficient 
the sewage will back up the sewer until sufficient head is 
obtained to produce the required velocity. Hence to prevent 


THE DESIGN. 


139 


this the fall in the siphon itself should be made great enough 
to create the velocity which will be required by the largest 
quantity to be passed at any time. 

An inverted siphon may at times be necessary for passing 
under some obstruction in the street—as a large conduit of 
one kind or another, but this should be avoided where 
possible. 

For details of inverted-siphon construction see Articles 49 
and 77. 


Art. 39. Sub-drains. 

Very frequently storm-sewers are placed at such a short 
distance from the surface that they cannot be utilized for 
draining damp cellars, particularly since a cellar should be 
connected with no sewer whose crown is above its level, from 
danger of back-water when the storm-sewer flows full. 
Ordinarily the house-sewer is below the cellar-level; but this 
should not be utilized as a drain, both because the amount of 
sewage may thus be too largely increased; and still more on 
account of the danger from sewer-air, which would have free 
access through the drain should the trap-seal evaporate during 
a drought, which it is very apt to do, and from the cellar this 
air might permeate the entire house. 

From a sanitary point of view the drainage of wet soils 
is almost, if not quite, as important as the sewerage and 
should not be neglected. The mere opening of sewer-trenches 
tends to drain the soil, even after they are refilled. But in 
many cases it is extremely desirable to provide other and 
more positive drainage. 

It is almost impossible to make a perfectly tight sewer 
without great expense, and when laid in wet ground sewer- 
joints may admit in the aggregate large quantities of water. 
This could be prevented and the land adjacent drained, to its 


140 


SEWERAGE. 


great improvement and the health of residents thereon, if this 
ground-water could be lowered along the trench by some 
means. 

During construction in wet ground much trouble will be 
experienced, even when the pumping facilities are ample, by 
water rising and flowing over newly laid inverts, to their per¬ 
manent injury (see Arts. 75 and 76). 

These difficulties can each and all be met in most cases 
by the use of sub-drains—that is, drains laid a little below the 
sewers. These are ordinarily laid in a narrow trench in the 
bottom of, and at one side or in the centre of, the sewer- 
trench. Their use for construction drainage will be consid¬ 
ered in Part II. When properly designed for this purpose 
their size will in most cases be sufficient for the continuous 
drainage of the land and also for cellar-drainage. The in¬ 
stances will be very few, however, in which any approach to 
an accurate estimate can be made of the amount of sub¬ 
drainage which will be required in a system. But provision 
should always be made for sub-drainage wherever the soil is 
wet, for permanent drainage if for no other purpose. 

The water flowing into such drains must have some outlet, 
and the most natural course would be, when the sewage is 
disposed of by dilution, to place the outlets of sewers and 
sub-drains at the same point. It may happen, however, that 
the necessity for sub-drains is not foreseen when the sewer- 
outlet is being built; or the place where they will be neces¬ 
sary may be so far from this outlet that a great length of 
otherwise useless drain-pipe must be laid to reach it; also the 
amount of ground-water may be so much greater than was 
anticipated, in spite of all investigations, that the drain-pipe 
near the outlet will not carry it all. In any of these cases 
another outlet may be desirable or necessary. This can fre¬ 
quently be found by leading the sub-drain in a special trench 
to a near storm-sewer or natural watercourse. In some 


THE DESIGN. 


141 

cases, however, special means must be resorted to, such as 
one of the methods of pumping (see Art. 42). 

If the sub-drain is necessary for construction purposes only 
it may be led to a sump-well where a pump is stationed, and 
broken and sealed at several points after construction is com¬ 
pleted. (This last will be necessary, as otherwise the drain 
would continue to lead the ground-water to this point, which 
might become permanently and dangerously water-soaked.) 

Although the sub-drain is in most cases smaller than the 
sewer, it must be laid at practically the same grade. The 
objection to flat grades in house-sewers does not apply to 
these so urgently, however, since the water flowing through 
them, after construction is completed at least, is usually free 
from suspended matter likely to cause deposits. The size and 
position, then, are the only elements of the general design to 
be decided upon. The size it will not be advisable to make 

r 

less than 6 inches at the outlet or for long stretches, but for 
stretches of a few hundred feet only and through ground but 
moderately wet 4- or even 2-inch pipe may be used. Pipe 
larger than 10 or 12 inches is seldom used in any but excep¬ 
tional cases. If a larger would be required (and instances can 
be named where the sub-drainage from a small town would 
more than fill a 36-inch pipe) special methods may be em¬ 
ployed; such as dividing the sub-drainage system into small 
sub-systems, each having its own outlet, which may, when 
constructed under a storm-sewer, discharge into the sewer 
immediately above it or which may be at a near water¬ 
course. 

Art. 40. House- and Inlet-connections. 

The connections between the sewers and opposite houses 
and storm-water inlets are of an importance second only to the 
sewer-mains. Any defect in one of the connections, while 


142 


SEWERAGE. 


limited in the range of its effect, is fully as detrimental within 
that range to the proper working of the system as a defect 
in the main itself. Since the house-connections are subject 
to extreme fluctuations of discharge and hence to stoppages, 
as also to the formation of grease deposits, it is desirable that 
they be equally as accessible as sewer-mains for both inspec¬ 
tion and cleaning, and also that their grade and alignment be 
given equal care in both the design and the construction. 
They should, if possible, be given a uniform grade of not less 
than 2 \io. Where the house sits back from the street an 
observation-hole (see Art. 47) should be placed at the fence¬ 
line, and one should be placed wherever there is a change in 
the line or grade. There should also be a hand-hole in the 
pipe just after it enters the cellar. The junction with the 
sewer should be made by means of branches, either Y or T. 
It should never be made in pipe sewers by breaking a hole 
into the shell and inserting a pipe. If the sewer be larger 
than 20- to 24-inch a T is advisable, both because this offers 
easier inspection of the house-connection from its lower end, 
which inspection can be made by a person entering the sewer, 
and because the branch can be placed entirely above the 
ordinary level of the sewage, which position it should occupy 
when possible so as to cause no interference with the sewage 
flow. When the sewer is too small to admit a man, which 
size will also not admit of raising the branch entirely above 
the ordinary sewage flow without giving it too steep a pitch, 
a Y branch is preferable, because this will retard the flow less 
than a T, and because the house-sewage will enter the sewer 
at a less angle with its flow. The vertical angle which the 
branch makes with the horizontal should not ordinarily ex¬ 
ceed 45 0 in small sewers, because of the interference with the 
flow and of the splashing caused by a vertical drop of sewage 
into their relatively small stream, and because of the danger 


THE DESIGN. 


143 


that the weight of the house-connection may break in the 
crown of the sewer. 

It is well to so place the branch in brick sewers that a 
trickling discharge from it will flow over the brick for the least 
possible distance, that deposits from such discharge may be 
avoided. In the case of combined sewers this would call for 
placing the branch but a short distance above the invert, but 
it should be given such a grade as to bring it higher than the 
crown of the sewer when it reaches the cellar. 

Some engineers always use T branches, more always use 
Y branches, for house-connections; but the practice here 
recommended seems to best utilize the advantages and avoid 
the disadvantages of each. 

The connections with inlets should never enter the sewer 
at an angle with its axis greater than 45°, on account of the 
great disturbance to the flow which would be occasioned. 
Where possible, and particularly in small sewer-mains, a 
manhole should be placed where each connection enters the 
sewer and the connection continued by a curved invert in the 
bottom of said manhole (see Plate VIII, Fig. 5). 

It is difficult to calculate the proper size for a storm-water 
connection, but, since there is little disadvantage in having it 
larger than is actually required, while the effect of too small 
a pipe may be disastrous, it is advisable to make the size fully 
ample to discharge all the run-off from the heaviest storms. 
A 12-inch pipe is probably the smallest which should ever be 
used; while a 24-inch may be required if the sewer lies near 
the surface (thus giving little fall to the connection) and if the 
tributary area is large. Where considerable undeveloped 
territory drains into the head of a sewer-main, or a small 
stream is there received, it may be necessary to continue the 
sewer to the inlet, not only not diminished in size but even 
enlarged into a bell mouth. It would be advisable to use an 


144 


SE WEE A GE. 


increaser at the upper end of every inlet-connection, since, 
owing to the churning of the water in the inlet, a “ standard 
orifice ” will not pass more than two thirds the water which 
can be carried by a pipe of the same size. 

Art. 41. Manholes, Inlets, Flush-tanks, etc. 

The necessity for frequent connections between the air of 
the sewer and the outer air has been shown (Articles 28 and 
29). As one means for this, and one which can always be 
adopted, manholes should be adapted to serve this end by 
having perforated covers. For this purpose, also, the more 
numerous they are the better. The other and greater neces¬ 
sity for their use, that of providing access to the sewers, 
should, however, have greater weight in fixing the distances 
which should separate them. It has been found in practice 
that a 6- or 8-inch sewer can be easily inspected and cleaned 
if this distance be not greater than 300 feet; a 12- or 18-inch 
sewer, when not more than 400 feet separates successive man¬ 
holes. A sewer which can be entered may, for this purpose, 
have its manholes even 600 or 1000 feet apart; but the cost 
and difficulty of cleaning are thereby increased, owing to the 
distance the material removed in cleaning must be carried 
through the sewer. Ventilation also is not so well served by 
so great intervals. It is better to fix 500 or 600 feet as the 
maximum distance between manholes on lines of the largest 
sewers. 

Economy would suggest placing a manhole at each sewer 
intersection, where it would serve both lines. This is also 
desirable as permitting a curved junction between the sewer- 
channels. Where a curved bend is made in the entire sewer 
a manhole should be placed at each end of the curve unless 
the sewer is sufficiently large to be entered. 

A manhole should be placed, in general, at each change 


THE DESIGN. 


145 


of line or grade, in order that every part of the sewer may be 
easily inspected. 

Economy will set a limit to the number of manholes which 
may be introduced; the number of the breaks in the street¬ 
paving caused by their covers it is also desirable to keep at a 
minimum. Principally for the first reason a manhole is some¬ 
times omitted in small sewers when it would come less than 
200 feet distant each way from another manhole, and a lamp- 
hole substituted. While the sewer cannot be inspected from 
this, a light can here be lowered into it to light up the sewer 

for inspection from the next manhole either way. Also a 

/ 

hose can be inserted at a lamp-hole for cleaning the sewer. 

The use of flush-tanks has already been discussed (Articles 
25-27). The grades of the laterals and the conditions of their 
use should be carefully examined to determine where fre¬ 
quent flushing will probably be needed. In some cases, such 
as where a flat grade on a long line of small sewer is unavoid¬ 
able, it may be desirable to place automatic flush-tanks at 
intervals of 800 to 1000 feet along its length, the tanks being 
placed at one side of the sewer and discharging into it 
through a short connecting-pipe. If automatic appliances are 
not employed no special tanks need be built in such a case, 
but manholes at intervals along the line can be used for 
flushing. 

All the local conditions should be examined that advan¬ 
tage may be taken of any opportunities for flushing offered 
by springs, streams, or any available sources of water, and in 
general decision made as to the places and methods of flush¬ 
ing. As a general rule every dead end of a house- or com¬ 
bined sewer should be flushed frequently and some arrange¬ 
ment for this placed at each such point. 

Inlets should be provided at frequent intervals throughout 
the area drained to receive the surface-water. In districts 
where the street traffic is considerable and where any great 


1 


146 


SEWERAGE. 


depth of water in the gutters would inconvenience a large 
proportion of the population the inlets should be not more 
than 200 or 300 feet apart, while in residence districts they 
may be so situated as to require the run-off to flow for 600 or 
700 feet over the surface. They should generally be so 
placed that all the run-off can reach them by flowing along 
the gutters only, and need not flow across the streets. The 
plan Plate V shows how this can be accomplished in most 
cases. Where this is impossible a culvert should be placed 
under the street-pavement in line with the gutter. 

Where street grades are continuous from one intersecting 
street to another inlets should be placed on street-corners. 
They are frequently placed at the gutter intersection; but a 
better plan in many cases, particularly on steep grades, is to 
place two openings, one just above each cross-walk, as this 
avoids the vehicle-trap caused by the ordinary corner inlet. 
Also an inlet should be placed at every point where two falling 
grades meet, and if this be between street intersections an 
inlet must be placed there on each side of the street. 

In the majority of cities a large proportion of the inlets 
are provided with catch-basins—more than the best practice 
would warrant, in the author’s opinion. The object of using 
a catch-basin is to retain there the silt and other heavy matter 
and not permit it to be carried into and deposited in the 
sewer. Catch-basins should be cleaned after every storm. 

The objection to catch-basins is that several days some¬ 
times must elapse—and several weeks usually do—between 
the beginning of a storm and the cleaning of the catch-basin; 
and during this time the organic matter which has been 
washed or thrown into the inlet, including horse-droppings, 
fruit and vegetable refuse, etc., is putrefying and frequently 
emitting objectionable odors. “ Such foulness is less offensive 
in the drains [storm-sewers] than in the catch-basins, which 
are situated at the sidewalks and where it is much more 


THE DESIGN. 


14 7 


likely to be observed. Also it is found impracticable to 
intercept all matter in the catch-basins which would deposit 
in the drains after they reach the flat grades in the lower part 
of your city. The cleaning of the drains would, therefore, 
be necessary in any event, and the additional amount of silt 
that would be intercepted by the catch-basins will not cost 
much more to remove. In the city of Paris, even though a 
combined system of sewers is used, it is not found objection¬ 
able to allow all the street-dirt to enter the sewers and there¬ 
fore the catch-basins at the inlets are omitted.” (Report of 
Rudolph Hering and Samuel M. Gray on Sewerage of Balti¬ 
more.) (See also Appendix No. I.) 

As a matter of fact catch-basins are not infrequently left 
uncleaned after light storms, or even heavy ones, for weeks 
together, and the odors from them are usually attributed to 
the sewers, which in most cases are far less foul. Moreover, 
catch-basins are usually cleaned with shovels only and suffi¬ 
cient filth left upon the sides and bottom to become noticeable 
by its odors. When cleaned so infrequently the catch-basin 
often stands full of material and is until cleaned practically 
non-existent so far as any useful effect is concerned. 

For these reasons the universal use of catch-basins is, in 
the author’s opinion, not to be advised, but rather the inlet 
should be so designed that all material shall at once reach the 
sewer. The inlet-connection he would also make without a 
trap, that it may assist in the ventilation of the sewer; and if 
the sewer and its appurtenances are properly designed, con¬ 
structed, and maintained there will be very few instances 
where any odor can be detected at the inlet. 

There may well be cases where catch-basins are desirable, 
as where the wash from a steep hillside is caught, or for other 
reason a large amount of coarse soil or “ clean dirt ” finds its 
way to the inlet; and there the catch-basin will need to be 
large, that but a small proportion of this may reach the sewer, 


148 SEWERAGE. 

and should be cleaned after every heavy shower. A small 
catch-basin is in most locations worse than useless. 

Catch-basins are also desirable where the sewer grades are 
very flat and the velocity is less than 3 feet per second; also 
on combined sewers where the streets are unpaved. 

Art. 42. Pumping of Sewage. 

There will frequently occur instances where, even if the 
sewers be laid at the flattest permissible grades, either the 
outlet will come too low, or the upper ends or some inter¬ 
mediate point will be too high for proper service. This is 
especially likely to occur where the outlet is at a considerable 
distance from the city; also where treatment of the sewage is 
necessary. Under such circumstances there is but one solu¬ 
tion of the difficulty—the sewage must be raised at some one 
or more points from a low to a higher level. (Where a street 
has not yet been graded or built upon it may often be prac¬ 
ticable to lay the sewer above the ground-surface in crossing 
a valley or basin, and so grade the street finally as to give it a 
proper covering, thus avoiding the necessity of pumping.) 

Where the sewage is discharged into tidal waters and the 
outlet is below high tide the lower stretch of the sewer will 
be filled twice a day, and the velocity therein cannot then 
exceed the quotient obtained by dividing the volume of 
sewage by the area of the sewer. It would therefore be well 
to make this sufficiently large for present needs only and 
duplicate it when greater capacity becomes necessary. In 
some instances tidal basins are constructed, which are closed 
—automatically in most cases—against the rising tide, and 
receive and hold the sewage flow during high tide, their con¬ 
tents being discharged on the falling of the tide. In some 
cases the sewers themselves are made sufficiently large near 
the outlet to serve as reservoirs in the same way. But these 


1 




THE DESIGN. 


149 




reservoirs are seldom satisfactory, owing largely to the diffi¬ 
culty of cleansing them from the deposits made while they are 
filled with stagnant sewage. It would be better, though of 
course more expensive, to pump the sewage during high tide; 
or better still to raise the streets and sewers generally, where 
this is possible, and discharge above high tide. (The city of 
Chicago some years ago raised the streets over its entire area 
to permit of better drainage.) 

In certain places the conditions are such that the water 
rises above the sewer-outlet, which is ordinarily free, for 
periods of days or even weeks; as on a lee shore during a 
storm or on rivers subject to extended floods. In such a 
case pumping is necessary; but the first cost of the plant 
should be kept at a minimum, since the interest on this will 
far exceed any saving that could be made in running-expenses 
for a few days. If possible it is well to locate the plant where 
power can be obtained from an outside source—as steam from 
the boilers of a water-works pumping-plant, electricity from a 
power or traction company, etc.—by which means both first 
cost and running-expenses may be reduced. 

Where house-sewage only is to be raised the apparatus 
should be of a capacity sufficient for the maximum flow. 
Storm-sewage, or at least the entire run-off from heavy 
storms, is not often pumped, owing to the enormous capacity 
required in the machinery. It will in most cases be found 
more economical to build special outlets for the storm-sewage 
to the nearest watercourse, where this is practicable. In the 
case of a combined sewer the house-sewage should all be 
pumped, as should even the run-off from light storms, which 
carries street-washings. But it will usually be permissible to 
allow the run-off from heavy rains with the admixture of 
house-sewage to escape by overflows and special storm-sewers 
to nearer outlets. If this would give rise to danger or a 
nuisance, owing to even the small proportion of house-sewage 


150 


SEWERAGE. 


contained, it is probable that the separate system should be 
employed, all house-sewage being pumped and each storm- 
sewer seeking the nearest outlet. 

In a very flat country it may be desirable to raise the 
sewage at a great number of points to prevent deep and 
expensive excavation. A sewer under a level surface, begin¬ 
ning at a depth of 8 feet and falling i foot in 300, would in 
2100 feet have a depth of 15 feet. Beyond this the cost of 
construction would rapidly increase unless the sewage could 
be lifted and started again at a depth of 8 feet. 

Whether the lifting of the sewage shall be done at one 
station or at several is usually a question of cost only. It 
can be exactly settled only by a comparison of the sum of the 
interest on first cost and the operating-expenses of one 
method as compared with another. (It is assumed that the 
depth of every sewer is made sufficient to meet all require¬ 
ments.) The fewer the lifting-stations and the further apart 
they are the greater will be each lift; also the greater will be 
the average depth of sewer. Hence, while the greater the 
distance between lifts the less will be the total cost of lifting 
machinery or apparatus, and also of maintenance of the same; 
on the other hand the greater will be the cost of the construc¬ 
tion of the sewer and also of its maintenance. The proper 
decision as to the number and location of the lifting-stations 
is frequently a problem requiring much careful study. While 
in one locality, where excavation is expensive, 5 feet may be 
the maximum lift which will be economical, in another this 
limit may reach 30 feet or more. If all the lifting can be 
done at one or two points it is usually most economical to so 
arrange it, even at great expense for excavation. 

The methods and apparatus to be employed may be: 
pumping by steam, gas, gasoline, or hot-air engines or electric 
motors, lifting by a Shone Ejector, an Adams Sewage-lift, 
or other appliance which seems adapted to the circumstances. 


THE DESIGN. 


151 

If steam, gas, gasoline, or hot air be employed a complete 
plant must be placed at each lifting-station. Where elec¬ 
tricity is the motive power a motor and pump only are 
required at each station. This renders possible a saving by 
using electricity, under certain conditions, such as many lift- 
stations with a small horse-power required at each, or even 
when the horse-power is considerable. For five stations at 
New Orleans, of very great pumping capacity, B. M. Harrod 
estimates the annual cost as follows: 

Steam. Electricity. 

Interest and depreciation.. $42,143 $58,684 


Operation. 69,960 54,825 

Total.$112,103 $113,509 


If the difference in cost of real estate for the two systems 
be allowed for, the annual cost would probably balance very 
closely.* 

The pumps usually employed are the piston- or plunger- 
pump and the centrifugal pump. Other devices have been 
employed, such as screw and oscillating pumps, but few with 
any success. The centrifugal pump requires a quite constant 
volume of sewage for its proper working; hence, usually, a 
storage-basin, which is objectionable. For ordinary lifts, how¬ 
ever, it is frequently more economical than a piston-pump; 
also the wear due to grit in the sewage is neither so great nor so 
injurious to the pump, and hence the necessity for screening 
the sewage is not so great as with the piston-pump. With 
the latter particularly care should be taken to remove all large 
solids and gritty matter. For this purpose gratings, wire 
screens, and settling-tanks are employed, the last being of 
such cross-section that the velocity through them is less than 
one foot per second. These should be near or in the pump- 

* Since the above was written electric pumping has been adopted for 
this work. 


\ 







152 


SEWERAGE. 


ing-station in order that they may be under the inspection of 
the engineer and that the deposits may be raised to the 
surface by power. If a steam-plant is used the screenings 
can be burned on specially prepared grates. 

The Shone Ejector is a device for raising sewage which is 
actuated by compressed air. It is usually employed where a 
number of lifting-stations are needed, and the compressed air 
for all is supplied through iron pipes from one air-compressing 
station. While the prime motive power, steam, is employed 
indirectly, the efficiency of compressor, air-pipe, and ejector 
combined is greater than if a number of separate steam- 
pumps are used, with either separate boilers ora central steam- 
plant, especially when the stations are numerous and widely 
scattered. For only two or three stations the economy of 
their use is doubtful. 

At Margate, England, sewage-lifts are used, with city 
water under considerable pressure as a motive power. 

At Aberdeen, S. Dak., two Worthington motors con¬ 
nected with a sewage-pump are driven directly by pressure 
of the water from an artesian well. The capacity is 3,500,000 
gallons per day, lifted 23 feet. 

The Adams Sewage-lift can be employed where the sur¬ 
face grade at some part of the system will admit of introduc¬ 
ing a drop, either vertical or on a steep grade through a pipe 
under pressure, in the line of some sewer or sewers. The 
sewage in making this drop transfers its energy by the • 
medium of compressed air through pipes to a lift-station. 
The more frequent application of the Adams lift, however, is 
in flat districts where city water is usually employed for com¬ 
pressing the air, the supply being controlled by a ball cock in 
a catch-basin at the lift-station. 

From none of these lifting appliances is there any odor, 
under good management. They can therefore be placed at 
any convenient point. The small pumping-plants, the Shone 


THE DESIGN. 


153 


Ejector and Adams Lift, are usually placed in vaults beneath 
the surface, the larger plants above ground. The sewage¬ 
pumping stations of London and Berlin are within the city 
limits, no odor whatever being perceptible near them. 

Art. 43. Intercepting-sewers and Overflows. 

It often happens that a town lies in a valley and upon the 
slope on one or both of its sides, and that while the valley 
district is too low to sewer to the outlet by gravity the upper 
districts are sufficiently elevated to do so. In such a case it 
would be useless to carry all the sewage to a main lying in 
the valley and raise it all to a gravity outlet-line. Instead 
a gravity-main should be run up each side of the valley at the 
minimum grade to receive all the sewage from higher up the 
hill, leaving only the sewage from below this to be pumped. 
Such a main is called an intercepting-sewer. 

In some instances a combined sewer is provided with an 
outlet to the nearest watercourse, which is for storm-sewage 
only, it being intended that the house-sewage shall be received 
and conducted away by another sewer, which also is called an 
intercepting-sewer. 

This term is also applied to a long sewer which passes 
down a valley and receives the sewage from several systems 
or parts of systems to conduct it all to a common outlet. 

It is frequently advisable, when the gravity-outlet must 
be below high tide, to locate an intercepting-sewer which can 
discharge above all tidal influence, that the effect of the seal¬ 
ing of the lower outlet may be felt by only a part of the 
system, the upper sections discharging through the free outlet 
of the intercepting-sewer. 

It sometimes happens that a system must be extended 
further in a given direction than was anticipated, or that the 
amount of sewage contributed by a district becomes greater 


154 


SEWERAGE. 


than the sewers can carry. This can be remedied by running 
an intercepting-sewer across such gorged sewers at mid-length, 
intercepting the sewage from above and leaving the lower 
lengths to carry only their local sewage. 

Where storm-water can find near outlets from many dis¬ 
tricts to a stream or other body of water, at which outlets, 
however, the house-sewage should not be discharged, an 
intercepting-sewer may be run along and near the water to 
intercept the house-sewage and convey it to a satisfactory 
outlet or to a disposal grounds or works. By a construction 
of the sewers called an interceptor ($ee Art. 48) the house- 
sewage and the run-off from light rains, which is the filthiest 
of storm-sewage, may be diverted to the intercepting-sewer, 
while the run-off from heavy storms will reach the nearer 
outlet. Mechanical contrivances for diverting the sewage are 
also used (see Art. 48). 

Another method of obtaining similar results is that of 
putting storm-overflows in the combined sewers, a special 
storm-sewer taking the overflow sewage to a convenient outlet. 
The overflow is, in general, an opening in the sewer with its 
bottom elevated some distance above the sewer-invert. Until 
the sewage reaches the height of this overflow it remains in 
the combined sewer and flows to its outlet; when the quantity 
becomes such that the height of sewage flow is greater than 
this the surplus discharges through the overflow into the 
storm-water outlet. It is usually so arranged that this shall 
occur only when the dilution of house-sewage by storm-water 
has reached the point where the discharge of the mixture into 
a stream is free from all danger. 

With either of these constructions the overflow or the 
interceptor should, if possible, be at such an elevation that it 
cannot be reached by floods or tides backing up the storm¬ 
water sewer. 



THE DESIGN. 


155 


Art. 44. Use of Old Sewers. 

In many cities, before any general sewerage system is con¬ 
structed or even thought of, short conduits, both private and 
public, have been built, discharging at the point nearest to 
hand—usually a stream or lake. These are often built in the 
crudest manner, graded by eye, and generally larger or 
smaller than necessary. In other cases the sewers are well 
built and graded and of a size adapted to remove the storm¬ 
water, but the outlet is located where house-sewage should 
not be discharged, or the sewer is not sufficiently deep to 
permit of receiving all house-sewage, or it is a pipe sewer and 
is not provided with sufficient branches for house-connections. 
Such sewers can frequently be incorporated into the proposed 
system, and a saving made of the cost and the tearing up of 
the streets avoided. But a thorough examination of them 
should first be made to ascertain which ones can be so used 
and how. 

If they are sufficiently large they should be entered and 
their condition learned as to size, grade, character of work¬ 
manship, etc. If the brick-work is very rough it may be 
desirable to clean it and plaster it with cement mortar. It 
may be cleaned by washing first with dilute muriatic acid, 
then with a solution of potash, and then with water. 

No connection-pipes should be allowed to protrude within 
the sewer. If the junctions are not well designed they should 
be torn out and rebuilt. If necessary a sufficient number of. 
manholes should be built to bring the intervals between them 
within the proper limits. If it is desirable to use an old cir¬ 
cular sewer as a combined sewer the invert can be narrowed 
as shown in Plate VII, Fig. 7. 

If the sewers are too small to be entered they should be 
examined thoroughly from the manholes by means of mirrors 
(Art. 68); pills (Art. 85) should be passed through them to 


156 


SEWERAGE. 


ascertain whether the bore is of uniform size and clear of 
deposits. Their size, grade, elevation, etc., should be learned 
by actual measurement. If they are not laid in straight lines, 
particularly those less than 12 or 15 inches in diameter, it is 
doubtful if they should be used, unless manholes and lamp- 
holes can be so judiciously located as to give straight stretches 
of sewer between them. 

If a pipe sewer is too high for efficient service or at too 
flat a grade a trench may be sunk along its line and the pipe 
taken up, cleaned, and the good ones relaid at a lower level 
or better grade in the same trench. In the majority of cases 
this probably will be the best disposition which can be made 
of old pipe sewers. 

Owing to the difference in character and volume of house- 
and storm-sewage a sewer not adapted for use as a house or 
combined sewer may often be used as a storm-sewer. It fre¬ 
quently happens that old combined sewers, or even the larger 
house-sewers, are admirably adapted to this use, and a 
separate system can then be built for the house-sewage. 

If an old combined sewer, or storm-sewer modified into a 
combined sewer as explained above, can be used, except that 
the house-sewage should be discharged at a new and more 
distant outlet, this sewage can be discharged through an 
interceptor, or diverted by a mechanical regulator into an 
intercepting house-sewer, and the old outlet used to discharge 
the storm-water only. 

But the efficiency of the system is of greater moment than 
small economies, or even large ones, and should not be sacri¬ 
ficed to them. 


CHAPTER VIII. 


DETAIL PLANS. 

Art. 45. The Sewer-barrel. 

Sewers have been made of almost every conceivable 
shape and the walls built of all kinds of materials. A few 
shapes and materials are of almost universal applicability, 
others are adapted to peculiar circumstances only, and some 
are freaks of invention adapted to no circumstances. 

The shape of cross-section is to a certain extent controlled 
by the material of which the sewer is constructed. The 
smallest sewers cannot be advantageously built of brick, but 
are usually composed of earthenware or metal pipes or of 
concrete. Earthenware sewers are made from 2 to 42 inches 
interior diameter. They are seldom made other than circular, 
owing to the liability of other shapes to become distorted in 
burning. Metal pipes are employed where the sewer will be 
under pressure, as in a siphon, or where there is a great deal 
of ground-water; also sometimes to better resist disturbing 
forces, as in made or treacherous ground or outlets under 
water or in shifting sands. The only metal commonly em¬ 
ployed is iron. Metal pipes have always been made circular, 
although there are none but economic reasons why other 
forms could not be made. 

Concrete and cement sewers are made of all sizes and 
shapes—circular, egg-shaped, rectangular, etc.—the smaller 
sizes being usually of cement, the larger of concrete 


i57 


i5» 


SEIVEEA GE. 


Wooden-stave sewer-pipe has been used in the West, and 
in the East to some extent. On the Los Angeles outfall 
sewer are 34,100 feet of 36- and 38-inch pipe of this descrip¬ 
tion. The outlet sewers in New York and Brooklyn are many 
of them creosoted wooden-stave pipe of 3 or more feet 
diameter. 

For all sewers the circle is the most economical shape, and 
generally the most desirable, if they are never to run less than 
| full, except that the use of platform foundations may 
modify the first statement. But if they are to be used as 
combined sewers the egg shape is to be preferred, or a form 
similar to Plate VII, Figs. 2 and 6. 

In Brooklyn, N. Y., and a few other cities cement sewer- 
pipe is used, and in general all sizes of this above 12 inches— 
in Brooklyn all sizes—are egg-shaped. Sections of this pipe 
are shown in Plate VI, Figs. 1 and 2. The flat base is given 
the pipe to prevent its rolling in the trench after being placed 
in position and to strengthen the bottom against crushing. 

In the case of large sewers, particularly those whose 
diameter exceeds 4 or 5 feet, it frequently becomes necessary 
to make the width greater than the height, because the depth 
of the invert is limited by sewer-grade requirements and the 
height of the arch by the street grade. A great number of 
shapes have been designed to meet these conditions. Some 
of the best are shown in Plate VI, Fig. 5, and Plate VII, 
Figs. 9 and 10. Plate VII, Fig. 4, shows a design for very 
low head-room, but the thrust of the arch is considerable and 
the side walls should be heavier than shown unless they are 
firmly backed by rock or solid earth. Plate VIII, Fig. 1, is 
a better design to employ where the head-room can be 
slightly increased. 

The use of steel beams for supporting the roof, with 
vertical side walls, as shown in Plate VII, Figs. 9 and 10, is 
becoming quite common, and is probably the best construe- 


DETAIL PLANS. 


*59 


tion for soft ground with limited head-room. Fig. 10 is 
adapted to storm-water only, or to a flow of house-sewage 
never less than 15 inches deep. The egg-shaped sewer in 
Fig. 9 is intended for the house-sewage, the larger channels 
for storm-water. 

Plate VIII, Figs. 2 and 3, show substitutes for egg-shaped 
sewers where the head-room is contracted. In Fig. 3 the 
semicircular invert should be sufficiently deep to admit of 
carrying the maximum house-sewage flow, that the sloping 
benches may not be fouled by it. Fig. 2 is especially adapted 
to an exceedingly variable house-sewage flow, as from a fac¬ 
tory district whose Sunday and holiday flow is inconsiderable. 

Plate VI, Figs. 5 and 9, Plate VII, Figs. 4, 5, and 10, 
and Plate VIII, Fig. 1, are best adapted to storm-sewage 
only, although they may be used as combined-sewer mains if 
the depth of the house-sewage flow is never less than 4 to 6 
inches at the shallowest part, and the velocity is then 
sufficient. Plate VI, Figs. 1, 6, 7, and 8, are intended for 
house-sewage only. In Fig. 7 the flat invert is permissible 
owing to the constant depth of the sewage flow, which con¬ 
sists of intercepted house-sewage from a number of residence 
suburbs. 

Plate VI, Figs. 2 and 3, Plate VII, Figs. 1,2, 3, 6, 7, 
and 9, Plate VIII, Figs. 2 and 3, are intended to act as com¬ 
bined sewers. In Plate VII, Figs. 5 and 6, the side bench is 
horizontal, that it may serve as a sidewalk for sewer inspectors 
and cleaners. 

The circular or egg-shaped form demands for strength a 
solid support under its invert. Where the soil is clay or firm 
loam, or a mixture of these with sand or gravel, or rock easily 
shaped, such a sewer may be built with walls of uniform 
thickness, the invert bearing upon ground shaped to receive 
it. If the ground is not firm, however, or cannot be readily 
shaped, the sub-invert spaces must be filled with concrete, 


SEWERAGE, 


160 


Plate VI. 




FIG. 8. SALT LAKE CITY. 
OUTLET SEWER. 
























































DETAIL PLANS. 


161 


brick, or stone masonry, as in Plate VI, Figs. 3, 5, 6, 8, 
and 9. If the arch is of such dimensions that the horizontal 
thrust becomes more than the soil can receive without yield¬ 
ing, then the side walls must be designed to receive this 
thrust, as in Plate VI, Figs. 5, 6, 8, and 9. The general 
principles of arches apply, of course, to arched sewers, one of 
the most important being the necessity for stiffness of the 
haunches. 

The circle, as has been stated, is the most economic shape 
for a sewer when the invert requires no backing. When this 
is necessary, however, the circle becomes an expensive shape, 
and the most economic is one with vertical side walls and 
bottom flat or conforming generally to the shape of the trench 
bottom. This is seen by an inspection of Plate VI, Figs. 6 
and 8, Plate VII, Figs. 4 and 10. It is for this reason that 
most of the flat-bottomed sewers are built. Permanency of 
construction demands a covering for timber platforms, which 
are liable to abrasion and also to rotting away. This cover¬ 
ing, forming the sewer bottom, is usually given a curved form, 
as in Plate VI, Fig. 5, or a sloping one, as in Plate VIII, 
Fig. 1, for two reasons: to concentrate small streams and 
decrease deposits, and to give strength to the bottom to resist 
the upward pressure which will exist when the soil is soft mud, 
quicksand, or similar material. 

The materials of which sewers are commonly composed 
are brick, stone, and concrete masonry, cement and vitrified 
salt-glazed pipe, and, under special conditions, cast- or 
wrought-iron or steel pipe. 

Stone and brick masonry is usually built up in cement 

/ 

mortar, and cement is always used for concrete. The stone 
masonry is usually rough, but compact and well-built, rubble. 
In arches brick is usually employed, as being cheaper and also 
stronger unless the stone are carefully dressed. The interior 
surface of the sewer, when this is built of stone, is usually 


SEWERAGE, 


162 


Plate VII. 



WASHINGTON D.C. STANDARD SEWERS. 



FIG. 4. TIBER CREEK, (Washington) 
SEWER IN 1893. 



«&gs - js &* ggtyj ri 1 ^ ^ vSScfr S *** -<^3 i^aigga 


-K-SP—?- 

,w 

CONCRETE 1 : 4: 8 


sgfU. 


CONCRETE 1:6:12 




ELG. 9. DOUBLE STORM CHANNEL AND HOUSE SEWER; BRUSSELS. 
UNDER RAILWAY TRACKS. 



FIG. 8. OLD LONDON ‘•‘SEWER 
OF DEPOSIT.” 


a^CONCRETE ANO i PLASTERING 




FIG, 10 . CANAL STREET SEWER; ST. PAUL, MINN. 








































































DETAIL PLANS. 


163 


lined with a 4-inch ring of brick, because a brick surface can 
be more easily made smooth than can stone masonry (see 
Plate VI, Fig. 9). If much wear is anticipated smooth- 
dressed granite or trap blocks are frequently used as invert¬ 
lining (see Plate VI, Fig. 8). 

Where the foundation is yielding a concrete base is fre¬ 
quently used under the sewer, as in Plate VI, Fig. 8, Plate 
VII, Fig. 9. But if it is soft a platform or even piles should 
be used under the concrete. 

Sewers built entirely of concrete have been used in 
Europe very extensively and are coming into use in this 
country. In many localities concrete is cheaper than rubble 
or brick masonry. If well made a concrete sewer is both 
stronger and tighter than a stone or brick one, and can be 
made more durable than many kinds of stone or brick. The 
wearing-surface should be given a smooth coat of rich Portland- 
cement mortar J inch to 2 inches thick, or a lining of hard 
brick, which is probably better owing to the liability of 
cement coatings to separate from the body of the concrete 
(see Plate VI, Fig. 6; Plate VII, Figs. 1 and 2).* 

If arches of small radius are built of brick-work laid with 
radial joints much cement is used, the arch is often weak, and 
the inner surface a polygon in section rather than a curve, 
unless brick especially shaped are used. If laid well such 
arches are also expensive in labor. To meet these objections, 
which apply particularly to inverts in egg-shaped brick sewers, 
invert-blocks of vitrified clay have been used. There are 
objections to these, the principal of which is that a joint 
entirely through the sewer is made, and where the hydrostatic 
head is greatest, which is almost sure to permit the leakage of 
water into or out of the sewer. They are also rather expen¬ 
sive, and are but little used now. A section of such a block 
is shown in Plate VI, Fig. 11. 

A better plan for constructing short-radius inverts is by 


* The use of expanded metal with concrete has recently been adopted 
with success for many large sewers. 




SEWERAGE . 


164 


Plate YIU. 



STEEL I BEAM 




STEEL I BEAM 



WOODEN OUTLET SEWER 
NEW YORK CITY. 


STEEL I BEAM 



0G.7. JUNCTION OF BRICK SEWERS. 




FIG. 5. JUNCTION MANHOLE. 



FIG. 6. JUNCTION OF 8 FT. AND 11 FT. SEWERS. 






FIG 8. 

HUB & SPIGOT JOINT, 


rrrr77^ 







xT///ziy 

FIG 9. 

RLNG JOINT. 



BEVEL JOINT. 



FI 

■‘archer" joint. 


































































































DETAIL PLANS. 


165 


the use of concrete or brick, lined on the inside with vitrified 
sewer-pipe split into thirds, which is approximately the arc of 
the small invert-circle in the egg-shaped sewer. Such a con¬ 
struction is shown in Plate VIII, Fig. 2. This construction 
is also well adapted to such sewers as are shown in Plate VII, 
Figs. 2, 6, and 7, Plate VIII, Fig. 3. 

Whole vitrified pipe are used for lining to circular sewers 
up to 42 inches diameter, when the pipe is not used alone on 
account of the additional strength or tightness of joints 
required. 

There is no fixed rule for the thickness of sewers, which 
depends upon the shape and diameter of bore, the material, 
the pressure received from the surrounding soil, and other 
circumstances. Brick sewers less than 30 inches diameter are 
frequently made but one ring—4 inches—thick; from this up to 
about 60 inches, 2 rings or 8 inches thick; from this up to 120 
inches, 3 rings or 12 inches thick. This applies to the arch 
more particularly, unless the surrounding ground is very firm, 
when the invert may be made of equal thickness, or even 8 
inches thick only when the arch is 12 inches or more thick. 
Some engineers never use less than two rings of brick in a 
sewer-arch; some use one ring up to diameters of 3 feet or 
more. The latter may give sufficient strength against crush¬ 
ing, but is hardly stiff enough to resist distortion except under 
unusually favorable circumstances. 

The thickness of the side walls, when these are vertical, 
must be such as to enable them to withstand the pressure of 
the soil without or of the water within the sewer when it is 
full; also to receive the thrust of the top arch when the soil 
is not capable of doing so. 

When two sewers intersect one or both should be curved 
in the direction of flow of the other. If one or both are small 
the curve may be made in a manhole (Plate VIII, Fig. 5). 
If one is many times larger than the other the curve may be 


SEWERAGE. 


166 

omitted, the branch making an angle of 45° with the main 
sewer at the junction. Where they are each larger than 30 
to 36 inches diameter the intersection should be made by 
bringing the two barrels gradually into one. This will require 
considerable skill in both design and construction when the 
tops and inverts are both arched. When the top is a girder 
construction the plan is much simplified, and still more so if 
the bottom also is flat. The crown of the sewer a short dis¬ 
tance below the junction should be as low as that of the lower 
of the two sewers a few feet above it. A plan of a junction 
of two circular sewers is shown in Plate VIII, Fig. 6. If the 
head-room is limited the plan shown in Fig. 7 may be used. 
In Wilmington, Del., the junction of two 6-foot and a 
io-foot sewer forms a chamber which is roofed with counter- 
groined arches. 


Art. 46. Pipe Sewers. 

Pipe is ordinarily used for sewers up to 18 or 24 inches 
diameter. Above this up to 42 inches vitrified clay pipe is 
sometimes used, but many engineers are doubtful of the 
strength of the larger sizes against crushing. The smaller 
sizes up to 18 or 24 inches, when made of good clay well 
burned, are sufficiently strong for ordinary locations, although 
the ** double-strength ” pipe (having a thickness of shell T \ 
the diameter) is recommended rather than those of the stand¬ 
ard thickness, which is less than the diameter by a differ¬ 
ence which increases with the diameter. It has so far been 
found impracticable to make good, sound, symmetrical clay 
pipe with shells much thicker than the diameter. It is 
probable that if this thickness be maintained the largest sizes 
of pipe are amply strong for ordinary circumstances. 

In many instances where vitrified clay pipe has been 
crushed in the ground it has been found that this was probably 


DE TAIL PLANS. 167 

due to the fact that the pipe had a bearing on the bottom at 
only one or two points instead of along its entire length, or 
that stones or frozen earth were thrown upon it in back-filling. 
If earth is well tamped under and around a vitrified clay pipe 
it will not usually collapse, even when broken, although it 
may leak. Such pipe ordinarily breaks along four lines—at 
top, bottom, and each side—into pieces of almost equal size. 
For this reason fire-cracks and slight imperfections which do 
not cause the rejection of a pipe should be placed at a point 
about 45 0 above the horizontal in laying, and not at the top. 

Several tests have been made of the strength of vitrified 
clay pipe. In one series, in which the pipe were bedded in 
sand and the load applied to the entire length of the top, 


8-inch pipe broke when the weight per foot of length was 1363 to 2256 pounds 

12 “ “ “ “ “ “ “ “ “ “ “ 1227 to 2756 

15 “ “ “ “ “ “ “ “ ..1261 to 2297 

18 “ “ “ “ “ “ “ “ “ “ “ 1464102093 


i i 
i i 
11 


From similar tests made in 1897 F. A. Barbour of Boston 

/i.6 5 

deduced the expression p — in which p is the pressure 

per lineal foot in pounds at the first cracking, t is the thick¬ 
ness in inches, d is the diameter in inches, and c =. 33,000. 

Tests made by T. H. Barnes on the strength of 12-inch 
vitrified clay pipe when acting as a beam between supports 2 
feet apart gave the following results: 


Thickness. 

Cracked at 
(Pounds) 

Broke at 
(Pounds) 

Equal to 

(Lbs. per Lin.Ft.) 

Remarks. 

i" 

IIOO 

2750 

1880 

Fire-crack 

I" 

2000 

2000 

1330 


i" 

2690 

2810 

1870 


i" 

2220 

245O 

1630 


I" 

2110 

2535 

1690 



The exact amount of pressure brought to bear upon a 
sewer by back-filling is uncertain. For a few feet of depth it 
probably bears the entire weight of the earth immediately 
above it. With granular material the proportion of pressure 















i68 


SE JVEEA GE. 


to weight of back-filling probably decreases but little, while 
with other soils it decreases more or less rapidly after the 
depth equals the width of the trench. But it is probable that, 
while the latter material gives an almost vertical pressure, the 
former acts more as a fluid, pressing normally to the surface 
of the sewer, and is not so liable to crush it. Little, however, 
is known on this point. From certain experiments in which 
natural conditions were only partially reproduced it was 
thought probable that for trenches io feet or more deep the 
percentage of weight of back-filling transmitted to the sewer 
equalled I — coefficient of friction of the material; that gravel 
transmits 36 per cent and wet clay 65 per cent of its weight; 
that up to 10 feet the percentage transmitted decreased from 
100 per cent as the square or cube of the depth. If the 
depth of covering is small there is danger that outside weight 
from road-rollers or even heavy wagons may crush it. But 
this danger appears to be very slight when the depth of 
covering equals or somewhat exceeds double the width of 
trench. 

The joints of vitrified clay pipe sewers are generally made 
of the bell-and-spigot pattern, as shown in Plate VIII, 
Fig. 8. The ring-joint (Fig. 9) is not now very extensively 
used, as its supposed advantages are found to be largely 
imaginary, while its disadvantages are not. It is almost im¬ 
possible to make tight joints with the ordinary ring-joint and 
the expense is greater. 

The joint of a bell-and-spigot pipe is made sometimes of 
clay, but in this country cement mortar is almost universally 
used. Clay has cheapness alone to recommend it as compared 
with cement. Other materials have been used for sewer-pipe 
joints, such as the Stanford preparation, a tar-and-sulphur 
compound. In Germany asphalt has recently been used and 
good results reported. Most of these materials are more 
expensive and less durable than Portland cement, and are 


DETAIL PLANS. 1 69 

probably to be preferred to it only under certain circum¬ 
stances, if at all. 

A glazed clay pipe offers a poor surface for cement to 
adhere to, and consequently with it an absolutely tight joint 
is almost impossible of construction. After a short period of 
use, however, a well-made joint of good cement will become 
so stopped with matter strained from out-filtering sewage as 
to be practically water-tight. But if the head of ground- 
water is greater than that of sewage the flow will be inward 
and the joint will probably not become tighter than it was at 
construction. Tighter joints could probably be made if the 
glazing were omitted or removed from the surfaces in contact 
with the cement. 

If much sewage leaks out through a joint there is danger 
that the remaining fluid will not be sufficient to keep the 
sewer clean of deposits. But, as just stated, such a condition 
seldom continues for a long time after the sewer is put into 
use if the joints were well made. 

Several modifications of the ordinary joint have been 
designed to overcome this difficulty, such as roughening the 
outside of the spigot end and the inside of the bell. One 
style of patent joint is shown in Plate VIII, Fig. 11. Such 
complicated joints are expensive and difficult both to manu¬ 
facture and to lay, and are seldom used. If there is consider¬ 
able ground-water it is better to lay the pipe as shown in 
Plate VII, Fig. 3, or to use light-weight or second-quality 
cast iron, or wrought iron or steel. Carefully made concrete 
or brick sewers may also be used for the larger sizes, of extra 
thickness to resist percolation. 

The amount of ground-water which may leak through a 
cement joint depends very largely upon the shape of the bell 
and the manner in which the joint is made. If the annular 
cement-space in the bell is too small the cement is likely to 
be improperly compacted therein or not to enter at all at 


SEWERAGE. 


170 

some points. Experiments seem to show that the deeper the 
ring of cement in the joint the less the leakage. If for any 
reason the cement draws away from either bell or spigot a 
leak is caused. Hence it seems best, particularly in wet 
soils, to use extra deep and wide sockets. The present 
standard of width is f inch for pipe from 2 to 10 inches 
diameter and -J- inch from 12 to 24 inches diameter, which, 
if always secured, should be sufficient. The depth of joint it 
would be well to have at least ij- inches greater than the 
thickness of the pipe; 2 inches would probably be better. 

With poor joints the amount of leakage may be limited 
only by the amount of ground-water, but with the best of 
cement joints in very wet ground the leakage may amount to 
5000 to 20,000 gallons per day per mile of sewer. In very 
many systems it is more than ten times this amount. 

Experiment seems to show that neat Portland cement 
makes the tightest joints, Portland cement and sand I : I 
the next, natural cement and sand I : I the next, and natural 
cement neat the most porous joint. 

Since the joint is the weak place in a pipe, the fewer joints 
there are the better. The expense of laying, also, is decreased 
by decreasing the number of joints. For these reasons the use 
of 3-foot rather than 2-foot lengths of pipe is advised. Vitri¬ 
fied clay pipes more than 3 feet long have not as yet been 
manufactured with success, but 3-foot lengths can be furnished 

by most pipe-manufacturers at the same price per foot as the 

« 

2-foot lengths. Some prefer to use the 2-foot lengths when 
the diameter of the pipe exceeds 15 or 18 inches, as the 3-foot 
lengths of the larger pipe would require a derrick for handling. 
Thirty-inch pipe is generally made 2 \ feet long. 

There are some advocates and users of cement sewer-pipe, 
the most important in this country being the city (now 
borough) of Brooklyn, N. Y., which has used it almost 
exclusively for 35 years or more. It has the advantage over 


DETAIL PLANS. 


171 

clay pipe that it can be moulded to exactly the size and shape 
desired, while the clay shrinks and sometimes warps in burn¬ 
ing. It is therefore possible to obtain a sewer with a more 
uniform bore by using cement pipe; also to obtain the advan¬ 
tage (not very considerable under most circumstances) of a 
flat base, as shown in Plate VI, Fig. 1. 

When this pipe is made of good cement and sand and this 
is properly proportioned and mixed it should give a material 
which will improve with age. It is, however, more difficult 
to detect the quality of a cement than of a vitrified clay pipe, 
and much worthless cement pipe has consequently been put 
upon the market. Clay pipe has a somewhat smoother sur¬ 
face, but this difference grows less with age, owing to the 
coating which forms on each. 

Cement pipe weighs from 50 to 100 per cent more than 
clay pipe of the same diameter, and hence both freight and 
expense of handling are increased. Good cement pipe is in 
most places more expensive than good clay pipe. 

Art. dT. Manholes, Lamp-holes, Flush-tanks, etc. 

The purpose of manholes, as the name implies, is to give 
admittance to the sewers, which is necessary for the purpose 
of inspection and cleaning. They should therefore be suffi¬ 
ciently large to permit the passage through them of a man of 
average size. 

Manholes are in general built immediately above a sewer 
and leading from it to the ground-surface. In the case of 
some large sewers in Europe they are built at one side of the 
sewer and connected with it by an underground passage, the 
chief advantages of which construction are the greater con¬ 
venience for entering and the avoiding of manhole-heads in 
the street-paving. But this construction is very expensive 
and the passage is liable to be a collector of filth. 


\J2 


SEWERAGE. • 


The size of vertical manholes is usually 24 inches, although 
sometimes only 22 or even 20 inches, diameter at the top, 
increasing towards the bottom to a size in which a man can 
work. The least size advisable for the bottom on lines of 
pipe sewers is 4 feet circular or 3 feet by 4 feet 6 inches 
oval. In manholes of this size the ordinary operations of 
inspection and cleaning of pipe sewers can be carried on. 
There is no particular advantage in having an ordinary man¬ 
hole of more than 5 feet interior diameter. 

Wherever possible the sides of the manhole should be built 
vertical from the side benches of the bottom (ab and cd, Plate 
VIII, Fig. 5) to a point 3 feet above, from which point they 
may be brought in with a straight batter to the smaller top, 
which is usually circular. Where the depth of the top of the 
sewer below the surface is less than 7 feet this construction 
becomes difficult, owing to the considerable angle which the 
upper walls must make with the vertical. The slope cannot 
well begin at a lower point than that stated and leave work¬ 
ing-room at the bottom. If the depth of sewer is more than 
5 feet this difficulty can be met by arching the walls (see 
Plate IX, Fig. 2), which construction requires careful work¬ 
manship. An alternative method, especially adapted to a 
depth of less than 5 feet, is to reduce the area of the manhole 
near the top by an offset, using either a brick arch or an iron 
beam to span the offset (see Plate IX, Fig. 3). If the man¬ 
hole is more than 10 feet deep the diameter should increase 
more rapidly for the first 3 feet down from the top, being at 
least 2 feet 9 inches at that depth, as otherwise descent 
through the shaft will be difficult. 

Descent through the manhole can be made by means of a 
ladder or a rope, but it is customary to build steps into the 
wall for this purpose. These may consist of protruding 
bricks or stones or cast- or wrought-iron pieces. The first 
offer but precarious footing, cast iron is not so reliable as 


DETAIL PLANS. 


173 


Plate JX. 




FIG. 2. SHALLOW MANHOLE. 


o 

.‘ E 



0 1 



^-S 5 -h 
. -L 






FIG. 5. CROSSING MANHOLE. 



iYzZ'-** 
FIG. 10. 

PIPE LAMPHOLE. 
< 10 *. 



FIG. 11. 

BRICK LAMPHOLE. 

















































































































































































174 


SEWERAGE. 


wrought and costs little, if any, less; the last is therefore 
recommended. These steps are made of various shapes. 
The simplest and probably as good as any is one made of a 
round bar bent as shown in Plate IX, Fig. 4. The steps 
should be placed about 15 inches apart vertically, and either 
directly under each other or alternating on each side of a 
vertical line, the former in narrow shafts. 

Manholes oval at the bottom are well adapted to locations 
where there are no intersecting sewers; those circidar, to 
points of intersection. 

Where one sewer crosses another without intersecting it 
a manhole of special construction, permitting of inspecting 
each sewer, is desirable. Such a one is shown in Plate IX, 
Fig. 5, in which the upper sewer is continued through the 
manhole by an iron trough. 

While at the junction of a pipe sewer-main and lateral the 
latter should be at a somewhat higher elevation than the 
former, the difference in elevation of the crowns of the two 
should not exceed 6 inches. To obtain this result the lateral 
may, if necessary, be lowered 2 or 3 feet at its end by increas¬ 
ing the grade from the previous manhole. If this would 
increase the depth of excavation by more than 3 or 4 feet a 
drop between the sewers may be made at the manhole. This 
should be so arranged that each sewer will be accessible for 
cleaning. The drop should not be made through the shaft of 
the manhole, but through a small smooth channel. A good 
design is that shown in Plate X, Fig. 8. 

When sub-drains are laid under large sewers arrangements 
for cleaning them may be made as shown in Plate VI, p'ig. 6, 
by a vertical branch opening into a manhole, or if they are 
under the centre of the sewer such a pipe may open into the 
sewer-invert, the opening being ordinarily tightly closed by a 
cap or plug. When the sub-drain is under a small sewer the 
branch pipe should lead into a manhole, opening either in the 


DETAIL FLANS. 


175 


Plate X. 




CENTRE SECTION. 


FIG. 1. FLUSHTANK 


1 H 


ANGLE 6A* 



GRATING 

FIG. 2. INLET. 



1 PIPE'THIMBLE 






OOOO 


O OO C5 

1 

O OOO 

j 

oo 

V 1 

OOOO 

O OOO 

1 

0000 

1 

1- 


FIG. 5. STONE TOP INLET 
WITH CATCH-BASIN- 


FLAGGING 




m- 



FIG. 4. 

WROUGHT [RON 
INLET GRATING^ 



INSPECTION HOLE 
GUARD, a. 



FIG. 8. DROP MANHOLE. 


FiG. 9. 

MANHOLE WITH SUBDRAIN 
INSPECTION HOLE. 


FIG. 7. DEEP-CUT 
HOUSE CONNECTION. 

































































































































































































176 


SEWEEA GE. 


sewer-invert or, better, in the bench. In either case the 
opening should be plugged so that absolutely no sewage can 
enter it (see Plate X, Fig. 9). 

Manholes of special design will be required by unusual 
conditions, but in all the three principal requirements of a 
manhole should be met: it should offer easy access to inspec¬ 
tion and cleaning of the sewer, and ventilation of the same; 
it should also be so proportioned as to resist the pressure of 
the surrounding earth. For this last purpose the curved form 
is better than the polygonal. 

Manholes for sewers larger than 30 to 36 inches are usually 
built up from the sewer-arch and have no special bottom con¬ 
struction. The sewer-invert under the manhole should be 
reinforced, however, if the ground is at all yielding. The 
manhole-shaft is sometimes placed on one side of the sewer 
both for strength and for facility of access (see Plate IX, 
Fig. 6). 

The foundation of a manhole should be perfectly solid. 
If the soil is soft a plank platform may be used. Owing to 
the irregular shape of the bottom concrete usually gives 
better results as to strength, shape, and imperviousness than 
does brick-work. The bore of each sewer should be continued 
through the bottom by a smooth channel of uniform section 
and slope, either straight or with a continuous curve. This 
channel can be plastered with Portland cement, lined with 
brick or with split vitrified pipe. The last method gives the 
smoothest surface and is the one most likely to give a straight 
channel of uniform size. For curved channels, if split bends 
of the desired radius cannot be had, brick plastered with Port¬ 
land cement is recommended. The channels should have 
vertical sides carried up to a point at least f as high above the 
invert as the top of the sewer-pipe, and benches should slope 
up to the sides of the manhole at an angle of at least io° or 
15 0 with the horizontal. 


DETAIL FLANS. 


177 


The manhole walls are usually built of brick, 8 inches thick 
from the top to a point 10 or 12 feet below the surface, and 
increasing in thickness with the depth. If the bottom is a 
circle or a well-designed oval with no radius greater than 6 
feet a 12-inch wall should be strong enough at any depth, 
unless the ground is a quicksand or similar material or is very 
wet. The outside of the manhole should be plastered with 
cement mortar to keep out ground-water or water used in 
settling the trenches, and to prevent the lifting of the top 
foot or two by freezing ground. 

The top of the manhole is generally capped with an iron 
casting sufficiently deep to permit the laying close to it of 
brick or stone paving. This will be about 8 or 10 inches 
except where the paving is made for heavy or city traffic, 
where it may need to be 12 or 18 inches. 

Whether the street is paved or not each manhole-head 
should be surrounded for a distance of at least 2 feet by stone 
or brick paving on concrete or sand foundation, the head 
being set £ to \ inch lower than the paving. 

The cover should be sufficiently strong to support the 
heaviest wheel-pressure. It should be provided with ventila¬ 
tion-holes giving as much area of opening as possible. Its 
upper surface should be roughened to provide foothold for 
horses. The ventilation-holes should be through the elevated 
rather than through the depressed parts of the cover, since by 
this construction the stoppage of the holes by dirt and snow 
and the entrance of dirt into the sewer are considerably 
lessened. Such a manhole-head and -cover, as used in 
Brooklyn, N. Y., is shown in Plate IX, Fig. 7. Covers are 
sometimes provided with locks to prevent the opening of the 
manhole by unauthorized persons. Much trouble is in some 
instances caused by these locks, particularly in freezing 
weather. A better plan probably is to make the covers so 


i;8 


SE WE A A GE. 


heavy that they cannot readily be raised without the use of 
some strong implement adapted to this purpose. 

More or less dirt will be sure to enter through the ventila¬ 
tion-holes and if allowed to reach the bottom of the manhole 
will tend, particularly in small sewers, to form stoppages. To 
prevent this a bucket of some kind should be suspended under 
the holes, smaller than the manhole-opening, that the air may 
pass up between the bucket and the walls, or a special con¬ 
struction of some kind should be designed for this purpose 
(see Plate IX, Figs. 8 and 9). These receptacles should be 
cleaned before they become filled with dirt, for which purpose 
the removable bucket of Fig. 8 is the more convenient. 
Another objection to Fig. 9 is the larger amount of street- 
surface occupied by the iron head. 

Lamp-holes may be from 8 to 12 inches in diameter and 
are placed vertically above the sewer. They are sometimes 
made by placing in the pipe-line a T branch pointing upward 
and resting a vertical line of sewer-pipe in it. This is 
decidedly poor construction, as the branch pipe is liable to be 
crushed by the weight. The upright pipes should be sup¬ 
ported by a foundation of brick or concrete or the entire 
shaft should be of brick. The latter is much to be preferred, 
since the pipe construction is almost sure to be pushed out of 
line by the settling of the back-filling. 

The foundation of a lamp-hole should be firm, the invert 
formed as shown in Plate IX, Fig. 11. The head it would 
be well to provide with ventilation-holes, but this is seldom 
done. 

A flush-tank should be tight. It should be so propor¬ 
tioned as to hold the required amount of water without 
increasing the head on the sewer beyond the limit set (Art. 
26). The flush-tank is usually set at the upper end of a sewer¬ 
line, toward which much sewer-air rises, and the sewer should 
therefore be provided at that point with ample ventilation. 


DETAIL PLANS. 


179 


In spite of this many flush-tanks are so built as to afford the 
sewer absolutely no ventilation, forcing the adjacent houses 
to unwillingly, and usually unknowingly, provide it. Since 
flushing-siphons cannot permit of ventilation through their 
passages, a vent should be furnished the sewer just below the 
flush-tank. It is advisable to combine with this a lamp-hole, 
as in Plate X, Fig. 1. A still better plan is to place a venti- 
lating-manhole just below, even in contact with, the flush- 
tank. 

Flush-tanks are usually built of brick with concrete 
bottoms, the whole being made water-tight. Concrete or iron 
would probably be preferable in some cases. 

The automatic flushing appliances in common use act on 
the principle of the siphon, the variations being in the method 
of starting the flow. Some have no moving parts whatever, 
such as the Rhoads-Williams and Miller tanks. Of those 
having moving parts the Van Vranken, which has a balanced 
tipping-pan at the foot of the siphon, is probably the best 
known. A number of other ideas have been used for flush- 
tanks, such as a tank on trunnions, which tips when full and 
returns to its original position when empty; a collapsing tube 
which, as the water rises in the tank, is extended upward by 
an attached float until it reaches its full length, when the 
water, still rising, overflows into and through it to the sewer, 
the tube meantime collapsing. 

The outlet of the flush-tank should be at some elevation, 
the more the better, above the sewer. If no automatic appli¬ 
ance is used the opening of the flush-tank may be in the 
bottom, stopped by a plug or cap, which is raised by an 
attached chain when the tank is full; or it may be in the side 
and be opened and closed by a valve, either sliding or hinged. 

If water is led to the flush-tank by a pipe this should be 
kept below the effect of frost, turning and rising to a higher 
level inside the flush-tank if necessary. 


i8o 


SEWERAGE. 


Inlets are made with and without catch-basins (see Art. 
41), and the openings are sometimes vertical, sometimes hori¬ 
zontal, and sometimes inclined. Their purpose being to 
admit water from the roadway to the sewer, the opening of 
each inlet should be sufficiently large to admit all the water 
which can reach it from the heaviest rain whose run-off the 
sewer is designed to carry. It may be so designed that a 
smaller one leading to a house-sewer shall pass the water from 
small rains or the first washings of a rain, while another larger 
one leads to a storm-sewer. The opening should be at the 
gutter where the water flows, and which may be slightly 
depressed at this point. If horizontal in the bottom of the 
gutter one large opening is not permissible, but smaller ones, 
into which neither carriage-wheels nor feet of horses or 
pedestrians can enter, must be used. The plate through 
which these holes are made must be able to support the most 
heavily loaded wheels which are likely to come upon it. But 
this need not include exceptionally heavy loads, which usually 
keep to the centre of the street. 

If the openings are through the face of the curb, in a plane 
either vertical or slightly inclined, they may be much larger. 
In some cases one large opening is used, entirely unprotected, 
through which children could and sometimes do fall. Except 
for this danger such a clear waterway is an excellent arrange¬ 
ment. But it is advisable to so place one or more bars across 
the opening as to remove the danger referred to. 

The total area of opening required may be found approxi¬ 
mately by the hydraulic formulas for flow through horizontal 
or vertical orifices or over weirs, as the case may be. In the 
case of openings less than 2 inches across in any direction an 
additional allowance should be made for the occasional 
stoppage of some of them by leaves, paper, etc. The vertical 
openings, being larger, are less liable to stoppage. If hori- 


DETAIL PLANS. 


181 


zontal openings in the gutter are in the shape of slots they 
should run across the line of the gutter. 

Between the openings and the sewer the channel should 
be straight or have as easy bends as possible, that the run-off 
may have an uninterrupted flow. The use of a catch-basin 
greatly interferes with this, the water seething and whirling 
in it during storms; consequently the channel connecting it 
with the sewer should be larger than if a simple inlet were 
used. In some instances a pipe leads directly from the open¬ 
ing to the sewer, either with or without a water-seal trap. It 
is better, however, to obtain a more substantial structure by 
setting under the opening a small basin with a curved bottom 
from which the pipe leads directly to the sewer. Where the 
opening is horizontal the basin is desirable to support the 
weight which may come upon the grating and, where a trap 
is used, to enable it to be placed below danger of freezing. 
It also facilitates inspection and cleaning of the connection- 
pipe (see Plate X, Fig. 2). Figs. 3 and 4 show two designs 
for inlet-gratings, the latter particularly adapted to admitting 
large quantities of water. 

A catch-basin usually consists of a well under the inlet¬ 
opening and below the connection-pipe to catch the heavier 
matters. It is sometimes placed between the inlet and the 
sewer on the line of the connection-pipe, and sometimes at 
the sewer in connection with a manhole. To be at all 
efficient it should extend more than 18 inches below the con¬ 
nection-pipe, since a heavy rain will keep the water in it so 
stirred up as to wash out any deposits above that point. 
The bottom of the catch-basin should be covered with a flag¬ 
stone or the most substantial of concrete- or brick-work. 

Inlet and catch-basin wells may be built of concrete or of 
stone, but are usually of brick. Catch-basin wells should be 
water-tight, that water may constantly cover the contents and 
lessen their odors. The gratings of catch-basins should be 


182 


SE WEE A GE. 


removable or the basins should be provided with manhole- 
openings and the wells be sufficiently large to be entered for 
the inspection and cleaning of the connection-pipes. 

When the inlet-opening is vertical the well is usually 
under the curbing or sidewalk, and access to it is through a 
manhole-opening in the sidewalk. There is a great variety of 
inlet-tops for such construction, both cast iron and stone 
being used. The latter, where not too expensive, is usually 
preferable, being neater, more durable, and usually more like 
the contiguous sidewalk material than cast iron. A stone- 
topped inlet is shown in Plate X, Fig. 5, an iron-topped one 
in Fig. 6. 

Traps are frequently placed in catch-basins or the con¬ 
necting-pipes to prevent the exit of sewer-air, unwisely the 
author thinks (see Art. 41). The outside trap is usually a 
running or P pipe trap. Many varieties of inside trap have 
been designed, both fixed and movable. The former should 
not prevent access to the connection-pipe and hence should 
be at least 15 inches from its opening. Traps with movable 
parts should be as simple as possible in construction and 
compel the outflowing water to make the least possible 
number of angular changes of direction. 

Instead of placing a catch-basin at each inlet it is some¬ 
times preferable to place silt-basins along the line of the sewer 
at intervals of 1000 feet or more, with a manhole over each 
for ventilation and cleaning. These are particularly applica¬ 
ble to flat grades of storm sewers in the separate system. 
They consist of an enlargement of the sewer, and a depression 
of a foot or more in its invert, into which the heavier silt is 
washed, and from which it can be removed more easily than 
when deposited along a stretch of sewer. These, however, 
should not be used to encourage deposit, but only when 
deposits would occur along the sewer if they were not pro¬ 
vided. Their advantage over inlet catch-basins is that the 


DETAIL PLANS. 


183 


odors reach the outer air further from pedestrians, and that 
the difficulty and cost of cleaning is not so great. They 
should be used in sewers which carry house-sewage in excep¬ 
tional cases only. Inlet catch-basins are generally preferable 
on lines of combined sewers where much heavy dirt reaches 
the inlet, or on storm-sewers where such dirt is washed in in 
very large quantities. 

Art. 48. Interceptors and Overflows. 

f 

The best form of interceptor to be employed is determined 
largely by the character of the system at the point of inter¬ 
ception. If the house-sewage is to be intercepted from tribu¬ 
tary sewers which originally discharged into a near body of 
water, the interceptor shown in Plate XI, Fig. 1, may be 
used. This “ leaping weir,” it is believed, was first used by 
Baldwin Latham about 1876. The exact length of opening 
required in the invert can be only approximately determined. 
It may be made smaller than is thought necessary and cut to 
the right size, which is ascertained by trial, after the sewer is 
in use. It will also probably be desirable to increase the 
length from time to time as the amount of house-sewage 
increases. The principal objection to this form of interceptor 
is that, although the storm-water may leap the opening, much 
of the sand and other heavy matter carried along the invert 
of the combined sewer will fall into the small intercepting 
sewer and be deposited there. 

An interceptor which meets this objection, but which may 
more properly be called a divertor, is shown in Plate XI, 
Fig. 2.* The flap-valve shown is closed by the rising of the 
float, which occurs when the amount of sewage becomes 
greater than it is desired that the house-sewer carry. The 
joints of the mechanism should be of bronze. A sewer does 
not offer the best conditions for the continued proper working 


* See Engineering Record, vol. xxxn, p. 41. 




184 


SE WEE A GE, 


Plate XX. 




FIG. 1. INTERCEPTOR (LEAPING WEIR). 



KNUCKLE JOINT 

B 


FIG. 2. INTERCEPTOR (DIVERTING) 



FIG. 4. 

BROOKLYN OVERFLOW 


VALVE 



FLAGSTONE 





VALVE g 

ft c 



y. 


--ft — A - 

' 




1 


FIG. 6.. INVERTED SIPHON. 


FIG. 5. INVERTED SIPHON 



FIG. 7. 
SUB-DRAIN, 




FIG. 8. 

SUB-DRAJN* 


FIG. 9. DEEP-CUT HOUSE 
CONNECTION IN FLOCK. 


FIG. 10. 

HOUSE CONNECTION 
INSPECTION HOLE. 




































































































































































































DETAIL PLANS. 185 

of any mechanism therein, but one so simple as this should 
give little trouble in its maintenance. 

When a sewer, because of improper designing or of 
changed conditions, becomes too small to carry all the sewage 
coming to it, the excess above its capacity may be diverted 
to and carried by a relief-sewer or -sewers. A relief-sewer 
may cross under and receive the excess from several gorged 
sewers, or a single sewer may overflow into several relief- 
sewers placed at intervals along its length and leading to 
near-by outlets. 

An outlet sewer-main to combined sewers is sometimes 
provided with overflow outlets at several points to avoid 
increasing the size of the main beyond the smallest necessary 
dimension, which is usually that which will carry sufficient 
storm-water to afford such dilution to the house-sewage as 
will render it unobjectionable to discharge this into an 
adjacent stream. The diversion into such a relief-sewer or 
relief outlet is ordinarily made by means of an overflow, con¬ 
structed as shown in Plate XI, Fig. 3, or as in Fig. 4, where 
the relief-sewer was constructed after the smaller sewers had 
long been in use. 

Art. 49. Inverted Siphons; Sub-drains; Foundations. 

Inverted siphons are usually circular in section, since 
always flowing full; usually of metal, since always under 
pressure, although the metal may be lined with brick or other 
material. The size required has already been referred to. 
When laid under water they should be so weighted or covered 
with earth or stone as to prevent their floating when pumped 
empty for inspection or cleaning, and should be absolutely 
tight. The inverted siphon is made sometimes to slope from 
both ends to a point near mid-length, sometimes with a 
vertical drop at one end, sometimes at both ends. The first 


SE WEE A GE. 


l86 

should be adopted only when the siphon is sufficiently large 
to permit the entrance of a man. When not of such a size it 
should be straight from end to end. This will usually require 
a shaft at one, sometimes at each, end, which may also serve 
as a manhole. It is in most cases advisable to place a catch- 
basin at the foot of such a shaft, although in place of this a 
basin in the bottom of an enlargement of the sewer just above 
the siphon is sometimes employed. A siphon with catch- 
basins is shown in Plate XI, Fig. 5, the valves on the ends of 
each siphon-pipe permitting either siphon to be closed to 
sewage and pumped out for inspection, while the other is in 
use. 

Unless a siphon under water is of large size and in tunnel 
or laid in a trench in a rocky bottom it should be protected 
from undermining by currents, or movement by shifting 
bottoms or channels. This protection is usually afforded by 
driving a row of sheet-piling on each side of the pipe, the 
space between these being in most cases excavated and filled 
with concrete. The softer the material in the bottom and the 
stronger the currents the deeper the sheeting should be 
driven. If the bottom is too hard to permit of driving sheet¬ 
ing, large stone rip-rap may be placed on both sides and over 
the siphon. 

A sewer must sometimes pass either under or over an 
obstruction—such as a water-main, another sewer, etc.—by a 
siphon, either inverted or erect. The latter requires greater 
care in construction and constant attention to maintain a 
vacuum at the summit, and the former is in the majority of 
cases the preferable construction. Such a siphon is usually a 
few feet in length only and under but little head. A man¬ 
hole should be placed over or near it when the sewer is 24 
inches or more in diameter, since it will probably need more 
frequent cleaning than the other parts of the line. If the 
sewer is less than 24 inches diameter a manhole should be 


DETAIL PLANS. 


1 87 


placed at the upper end of the siphon (which should be 
straight from end to end), and at the lower end also, although 
a lamp-hole may be substituted here if the siphon is not over 
150 feet long, and makes only an angle and not a vertical rise 
at this point. For such a case see Plate XI, Fig. 6. 

Sub-drains are placed either directly beneath the sewer or 
at one side of the trench. When there are no artificial foun¬ 
dations under the sewer the latter position is to be preferred, 
but is in some instances much more difficult and expensive, 
particularly in quicksand. The sub-drain should be sur¬ 
rounded with broken stone or clean gravel, varying preferably 
from the size of a hickory-nut to that of a pea. There should 
be at least 3 inches of this under the drain and 6 inches at its 
sides and top. In quicksand or similar material these dimen¬ 
sions should be increased 50 to 100 per cent. This stone 
should be well compacted to prevent future settlement. The 
joints of the drain should be slightly open and a 5- or 6-inch 
strip of cheese-cloth or burlap wrapped around the pipe at the 
joint to keep out the dirt. Or, if bell-and-spigot pipe is 
used, a piece of jute may be calked loosely into the joint for 
this purpose. 

If a sewer were laid directly over this there would be 
danger of a settlement of the same and of leakage resulting. 
For this reason the sub-drain should be laid at one side of the 
trench when the soil is firm, as in Plate XI, Fig. 7. In quick 
or running sand this is practically impossible unless the trench 
is very wide or unless close sheathing be driven on each side 
of the sub-trench and carried below its bottom; such sheath¬ 
ing not to be removed after the sub-drain is laid. It would 
usually be better and cheaper than this to lay the sub-drain 
in the centre of the trench (which must of course be close- 
sheathed in quicksand), and on the stone filling, when levelled 
off, to place a continuous platform on which to lay the sewer. 
Such construction is shown in Plate XI, Fig. 8. A still 


188 


SEWERAGE. 


better construction in any but firm soils is to lay a pipe sewer 
in concrete, as in Plate VII, Fig. 3. Where a foundation is 
necessary for the sewer the sub-drain construction is easily 
arranged. See Plate VI, Fig. 6, and Plate VII, Fig. 10. 

The sub-drain should be laid to grade as carefully as the 
sewer itself. It is seldom that a sub-drain can be so arranged 
that inspection can be made of it, and therefore perfectly 
straight alignment is not necessary; but there should be no 
sharp angles in its line, which might cause obstructions or 
interfere with the future cleaning of it. If cellars and base¬ 
ments are to be connected with this drain Y branches should 
be inserted to permit of such connections, and should be 
covered similarly to the house-sewer branches. 

When house or combined sewers are placed with their tops 
more than 4 or 5 feet lower than the average cellar depth in 
that locality it is advisable to place a standing house-connec¬ 
tion above each branch, bringing it to within 3 to 5 feet of 
the average depth of the cellar bottoms, but stopping at least 
7 or 8 feet from the surface. This is to avoid compelling 
each householder along the line to dig down to a deep sewer 
branch in order to make a connection. These standing con¬ 
nections are built while the sewer-trench is open, and are 
covered at the top with a cap or cover similar to house- 
branches. They should not merely rest in the branch, but a 
foundation of concrete or brick masonry should support each. 
The vertical pipes should be held in place during back-filling, 
as by stakes driven into the bank. In the case of a rock cut, 
or where the banks are not firm, the standing connection may 
be inclosed by a vertical trough of planks, between which and 
the pipe earth is packed, this trough being held firmly in 
place until the trench is filled and tamped. If the banks are 
liable to cave, sheathing should be driven at each such con¬ 
nection, and neither it nor the braces removed when the 
trench is filled. A standing house-connection in firm soil is 


DETAIL PLANS. 189 

shown in Plate X, Fig. 7. One in a rock cut is shown in 
Plate XI, Fig. 9. 

A sewer in soft soil, like any other structure, requires a 
foundation. Since the weight is not comparatively great the 
service of the foundation is more often to distribute the pres¬ 
sure and prevent local settling or heaving than to prevent the 
subsidence of the sewer as a whole. This purpose is usually 
achieved by use of a cradle (Plate VI, Fig. 4) or a platform 
of plank (Plate VI, Fig. 5), the former in comparatively firm 
soils like damp sand or loam, the latter in swamp-muck, 
quicksand, etc. Where muck or other soft, water-sogged soil 
is encountered it may be necessary to drive piles and rest a 
timber platform upon these. Such a foundation is shown in 
Plate VI, Figs. 3 and 6. Where a platform is used it is 
necessary to fill the sub-invert spaces of the sewer with 
masonry. All sewers in soft soils should have their inverts 
arching downward to resist the upward thrust of the ground 
between the side walls, since the weight of the masonry is 
largely concentrated in these walls. 

In rock excavations no part of the pipe sewer should come 
within 6 inches of the rock bottom, and the space between 
this and the sewer should be filled with sand or gravel 
thoroughly tamped to prevent settlements of the invert; or the 
pipes should be bedded in concrete, in which case the rock 
may be taken out only to the under side of the pipe. If the 
sewers are built of masonry this should be carried to rock 
everywhere under the invert. 


CHAPTER IX. 


SPECIFICATIONS, CONTRACT, ESTIMATE OF COST. 

Art. 50. Definition and Classification of Specifica¬ 
tions. 

Public work is frequently, if not in the majority of cases, 
done by contract by a “ party of the second part ” who is 
paid for this work by the city, the “ party of the first part.” 
That the contractor shall do the work as the city desires it is 
necessary that he be instructed what is desired and that he 
bind himself to follow the instructions. This should all be 
recorded in writing for the protection of both the city and the 
contractor. The agreement to perform the work on the one 
hand and to pay for the same on the other is called a contract 
and is generally accompanied by a bond under which the con¬ 
tractor places himself to perform the work as directed. 

The directions, called “specifications,” “consist of a 
series of specific provisions, each one of which defines and 
fixes some one element of the contract. These clauses relate, 
in general: first, to the work to be done; second, to the 
business relations of the two parties to the contract.” 
(Johnson’s “ Engineering Contracts and Specifications.”) 
The clauses in specifications for sewer construction referring 
to the work to be done may be classified as those: first, 
defining the character of the material to be employed; 
second, giving directions, dimensions, etc., for excavating 


SPECIFICATIONS , CONTRACT, ESTIMATE OF COST. IQI 

and back-filling; third, setting forth the methods to be 
employed in the construction of the sewer-barrel and appur¬ 
tenances, including foundations; fourth, stating the require¬ 
ments of the completed work, tests to be made, etc. ; fifth, 
giving general directions for the conduct and maintenance of 
the work, employment of labor, etc. Disposal plants will 
require separate specifications, varying with the character of 
the disposal employed. No general form for such can be 
given. Other special features of a system will call for special 
clauses. 

The clauses relating to the business relations of the two 
parties to the contract may be classified as relating to: first, 
time of commencement and of completion and rate of prog¬ 
ress of the work; second, character of labor and appliances 
to be employed ; third, measurement of and payments for the 
work; fourth, contractor’s protection of and responsibility 
for lives and property; fifth, abandonment, cancellation, 
assignment of contract, etc.; sixth, definition of names and 
terms employed. 

The specifications are generally accompanied by a set of 
plans which form a part of the specifications and contract. 
These together should set forth the work to be done so clearly 
as to leave no point for future dispute. Care should be taken 
that contradictory instructions are not given, but that all 
parts of both plans and specifications mutually agree. Too 
great profuseness should be avoided as confusing to con¬ 
tractor, inspector, and engineer. Many engineers insert pro¬ 
visions which they have no intention of enforcing under 
ordinary conditions, merely to be on the safe side, or which 
aim at theoretic perfection of details which cannot be attained 
in practice (of which fact their inexperience may make them 
ignorant). The fact that some clauses in a specification 
cannot be enforced is apt to detract from the effectiveness of 
the others. It is better to make only such requirements as 


192 


SE fVEEA GE. 


experience shows are desirable and practicable and give the 
contractor to understand that these will be rigidly enforced. 

No foresight can predict all the emergencies which may 
arise in sewer construction. To provide for these it must be 
agreed that the engineer can modify plans or methods of work 
during construction, as well as increase or decrease quanti¬ 
ties. Work not at first specifically provided for may be made 
the subject of separate contract, or if but small in quantity 
may be done under the original contract as extra work, to be 
paid for at its cost plus such a percentage for profit (generally 
10 or 15 per cent) as is fixed in the contract. 

Art. 51. Specifications for Materials. 

A set of specifications for sewer construction will be given 
and discussed in the succeeding pages. Some alterations and 
additions will probably be required to adapt them to any par¬ 
ticular case, but it is thought that they will be of considerable 
service as an illustration of both matter and form. Clauses 
in brackets are given as alternatives, the one preferred by the 
author being placed first; the same also holding true with 
reference to the lettered paragraphs. 

Paragraph 1. a. Sewer-pipe. —All pipe and specials, 
unless otherwise specified, shall be of the best quality, 
salt-glazed, vitrified clay sewer-pipe of the hub-and-spigot 
pattern; both body and bell shall [have a thickness not less 
than T \ the inside diameter of the pipe] [be of standard 
thickness]. Each hub shall be of sufficient diameter to 
receive, to its full depth, the spigot end of the next following 
pipe or special without any chipping whatever of either, and 
also leave a space of not less than one half inch all around for 
the cement-mortar joint; it shall also have a depth from its 
face to the shoulder of the pipe on which it is moulded at 
least 2 inches greater than the thickness of said pipe. Straight 


SPECIFICATIONS , CON TP ACT, ESTIMATE OF COST. 193 

and curved pipe having diameters up to and including 15 
inches shall be furnished in 3-foot lengths. Branches may be 
in 2-foot lengths. All pipe and specials shall be sound and 
well burned, with a clear ring, well glazed and smooth on the 
inside and free from broken blisters, lumps, or flakes which are 
thicker than ^ the nominal thickness of the pipe and whose 
largest diameters are greater than the inner diameter of said 
pipe; and pipe and specials having broken blisters, lumps, and 
flakes of any size shall be rejected unless the pipe can be so 
laid as to bring all of these defects in the top half of the 
sewer. No pipe having unbroken blisters more than \ inch 
high shall be used unless these blisters can be placed in the 
top of the sewer. Pipes or specials having fire-checks or 
cracks of any kind extending through the thickness shall be 
rejected. 

No pipe shall be used which, designed to be straight, 
varies from a straight line more than ■§■ inch per foot of length; 
nor shall there be a variation between any two diameters of a 
pipe greater than the nominal diameter. 

No pipe shall be used which has a piece broken from the 
spigot end deeper than inches or longer at any point than 
\ the diameter of the pipe; nor which has a piece broken from 
the bell end if the fracture extends into the body of the pipe, 
or if its greatest length is greater than £ the diameter of the 
pipe, or if such fracture cannot be placed at the top of the 
sewer. Any pipe or special which betrays in any manner a 
want of thorough vitrification or fusion or the use of improper 
or insufficient materials or methods in its manufacture shall 
be rejected. 

(Many engineers specify a depth of bell only 1 inch “greater 
than the thickness of said pipe,” but it is difficult to make 
tight joints in actual practice with such bells. Frequently the 
defects of sewer-pipe are not referred to in detail , but the 


194 


SE WERA GE. 


acceptance or rejection made optional with the engineer or 
inspector. 

If cement pipe is used the following paragraph may be sub¬ 
stituted for i. a.) 

Paragraph I. b. Sewer-pipe. —All pipe and specials,, 
unless otherwise specified, shall be of the best quality of 
cement sewer-pipe, of the [hub-and-spigot] [bevelled-joint] 
pattern; it shall have a thickness not less than inch plus 
y 1 ^- the diameter of the pipe. [Each hub shall be of sufficient 
diameter to receive, to its full depth, the spigot end of the 
next following pipe or special, without any chipping whatever 
of either, and also leave a space of not less than \ inch all 
around for the cement-mortar joint; it shall also have a depth 
from its face to the shoulder of the pipe on which it is 
moulded at least I inch greater than the thickness of said 
pipe.] [The bevel on each pipe shall be at least 25 per cent 
longer than the thickness of said pipe, with an even and firm 
edge.] 

All pipe shall be in 3-foot lengths and in section shall 
truly correspond to their nominal shapes. Each pipe shall 
have a flat base making exact right angles with the vertical 
axis of the pipe and with a width equal to f the interior 
horizontal diameter of said pipe. The inside surface of the 

N 

pipe shall be smooth and true, and no pipe shall be patched 
with cement or otherwise. Any pipe will be rejected which 
is not of fine, sound, and dense material throughout, or which 
shows the use of poor materials or imperfect mixing or com¬ 
pacting. 

Paragraph 2. a. Drain-pipe. —Pipe for sub-drains shall be 
of vitrified clay sewer-pipe in 1- or 2-foot lengths [of the hub- 
and-spigot pattern] [without bells or sleeves]. It shall com¬ 
ply with the specifications for sewer-pipe in so far as these 
refer to thickness, quality, and vitrification of material,, 
blisters, lumps, flakes, cracks, and breaks; except that the 


SPECIFICATIONS, CON TP ACT, ESTIMATE OF COST. 195 

engineer may at his option accept pipe having small fire- 
cracks or checks. 

Paragraph 2. b. Drain-pipe. —Pipe for sub-drains shall be 
composed of the best quality of drain-tile of [circular] [horse¬ 
shoe] cross-section in [one-] [two-] foot lengths. They shall 
be hard-burned and without cracks or any considerable de¬ 
parture from their nominal shape, size, or cross-section. 

Paragraph 3. Brick.— For all brick-work none but the 
best quality of sound, hard-burned, perfect-shaped bricks, 
presenting a regular and smooth surface, shall be used. After 
being thoroughly dried and immersed in water for 24 hours 
they shall not absorb more than 10 per cent by weight of 
water. Shale brick, if used, shall be composed of rock 
thoroughly ground and shall be homogeneous throughout and 
uniformly burned. 

Paragraph 4. Paving-stone. —This shall consist of hard 
granite or trap-rock, uniform in grain and texture. The 
blocks must be rectangular in form, not less than 3 nor more 
than 4 inches in either length or breadth, nor less than 4 nor 
more than 5 inches in depth, and so split and dressed with 
true surfaces that on neither top, ends, nor sides shall there 
be a projection from the general surface exceeding J inch. 

(This stone is used for inverts where there is excessive ve¬ 
locity in the sewer or impact from falling water.) 

Paragraph 5. Masonry-stone. —Stone for foundations 
and backing shall be of a sound and durable quality, free from 
cracks and seams, having top and bottom beds approximately 
parallel. No stone shall be less than 4 inches thick, 12 
inches long, and 8 inches wide. 

Paragraph 6. Iron Castings. —All iron castings shall be 
made from a superior quality of gray iron, remelted in the 
cupola or air-furnace, tough and of even grain, and shall 
possess a tensile strength of not less than 18,000 pounds per 
square inch. Test-bars of the metal 3 inches by % inch, when 


196 


SEWERAGE. 


placed upon supports 18 inches apart and loaded in the 
centre, shall have a transverse breaking load of not less than 
1000 pounds, and shall have a total deflection of not less than 
f inch before breaking. These test-bars shall be poured from 
the ladle at any time the engineer directs, before or after the 
castings have been or while they are being poured. All 
castings shall conform to the shape and dimensions shown 
upon the drawings and shall be clean and perfect, without 
blow- or sand-holes or defects of any kind. No plugging or 
other stopping of holes will be allowed. The castings shall 
be thoroughly cleaned of all lumps and subjected to careful 
hammer tests, after which they are to be dipped in a bath of 
coal-tar pitch heated to at least 200° Fahr. 

Iron pipe shall comply with the above specifications, 
except that the engineer may, at his option, receive a pipe 
having a limited number of small sand- or blow-holes on its 
exterior surface. No portion of the shell of the pipe shall 

have a less thickness than-( this thickness can generally be 

made the least which will permit of handling of the pipe with - 
out da 7 iger of breaking it , and non-uniformity of shell is not 
objectionable if payment is not made by weight). 

Paragraph 7. Wrought Iron. —All wrought iron must be 
tough, ductile, and fibrous, of a uniform quality, free from 
crystalline structure, cinders, flaws, or cracks. In bars it 
must have an ultimate strength of 50,000 pounds per square 
inch. Iron which has been burnt in the forge will be rejected. 
Each wrought-iron piece furnished shall correspond in all 
respects to the dimensions specified. 

Paragraph 8. Sand. —All sand shall be clean, sharp, and 
free from loam, clay, or vegetable matter. It shall not be so 
fine that each grain on the surface of a pile cannot be readily 
noted with the naked eye, nor shall it be exceedingly coarse 
when used for brick masonry. 

(Dirt in sand can usually be detected by rubbing a small 



SPECIFICATIONS , CONTRACT, ESTIMATE OF COST. 197 

amount on the palm, which will be soiled by any clay or loam 
present.) 

Paragraph 9. Cement. —Unless otherwise specified all 
cement shall be of the best quality of natural cement, and 
when tested neat in briquettes (Am. Soc. C. E. standard) 
shall show a tensile strength of at least 75 pounds after 1 hour 
in air and 23 hours in water and of at least 150 pounds after 
I day in air and 6 days in water. Cement for brick masonry 
or pipe-joints, when these are laid in wet ground, shall be 
quick-setting and show a tensile strength of at least 100 
pounds per square inch after 24 hours. Pats of neat cement 
made on glass and brought to a thin edge shall show no checks 
after setting in boiling water. 

When.specified Portland cement shall be used. This shall 
show a tensile strength of at least 400 pounds per square inch 
in a 7-day test made as above, and pats of the same shall 
show no checking. The cement mixed neat and stiff into 
pats i inch thick shall develop “ initial ” set in not less than 
20 minutes and “ hard ” set in not less than 45 minutes after 
mixing, except in the case of quick-setting cement to be used 
as specified above. 

The engineer shall be allowed to test all cement and notice 
of its receipt by the contractor must be made to the engineer 
at least 48 hours in advance of its use upon the work. Any 
cement not satisfactory to him shall be at once removed from 
the work. 

> . . 

Paragraph 10. Packing. —Packing may consist of flax, 
jute, oakum, or hemp, clean and with long fibres loosely 
twisted into strands. 

Paragraph 11. Timber. —All timber and planking used 
in cradles, platforms, and foundations shall be of spruce, or 
timber equally as good, straight, sound, free from sap, shakes, 
large, loose, or decayed knots, worm-holes, or other imper¬ 
fections which may impair its strength or durability. Piles 


198 


SE WEE A GE. 


shall be of sound, straight, live spruce or yellow-pine timber, 
of lengths specified by the engineer for each locality. They 
shall be not less than 6 inches in diameter at the smaller end. 
The bark shall be removed in all cases. 


Art. 52. Excavation. 

Paragraph 12. Classification of Materials. —All ma¬ 
terials excavated shall be classified as either earth or rock. 
No material shall be classified as rock which cannot be 
removed more cheaply by drilling and blasting than by pick¬ 
ing, except that any boulder measuring ^ cubic yard or more 
shall be so classified, whether blasted or removed bodily; but 
such boulder shall not be returned to the trench without being 
first broken up. 

Paragraph 13. Excavation of Trench. —The trench shall 
be excavated along the line designated by the engineer and 
to the depth necessary for laying the sewer or sub-drain at the 
grade given by him. In the case of pipe sewers it shall be 1 foot 
wider at the bottom than the outside diameter of the pipe, 
and for brick sewers as wide as the greatest external horizon¬ 
tal width of the structure to be placed therein, without any 
undercutting of the banks. Where, in the opinion of the 
engineer, the original earth is sufficiently compact and solid 
for the foundation of the work the contractor shall excavate 
the bottom of the trench to conform to the external form and 
dimensions of the invert or foundation as ordered. For pipe 
sewers the bottom of the trench under each bell shall be so 
hollowed out as to allow the body of the pipe to have a bear¬ 
ing throughout on the trench bottom and permit of making 
the joint. In case a trench be excavated at any place, 
excepting at joints, below the proper grade it shall be refilled 
to grade with sand or loam thoroughly rammed, without 


SPECIFICATIONS , CON TP ACT, ESTIMATE OF COST. 199 

extra compensation unless the extra excavation was ordered 
by the engineer. 

The material excavated shall be laid compactly on the 
side of the trench and kept trimmed up so as to be of as little 
inconvenience as possible to the travelling public and to 
adjoining tenants. Where the street is paved the paving 
shall be kept separate from the other material excavated. 
{It is generally desirable to place the paving material on the side 
of the trench which is to be left open for travel , and the earth 
upon the other.) All streets shall be kept open for travel and 
the engineer reserves the right to require the use of excavat- 
ing-machinery if necessary to insure this. 

No tunnelling will be allowed except by written permit, 
with restrictions, from the engineer. When tunnelling, the 
contractor will excavate the material to such cross-section as 
may be designated, using timbering or other tunnel-lining and 
shoring satisfactory to the engineer. The location and size 
of any shafts, and the location of pumps, derricks, boilers, 
and other machinery, must be approved by the engineer {see 
Art. 6 <f). The engineer shall have the right to limit the 
amount of trench which shall be opened or partly opened at 
any one time in advance of the completed sewer, and also the 
amount of trench left unfilled. 

The contractor shall not, without permission from the 
engineer, remove from the line of the work any sand, gravel, 
or earth excavated therefrom which may be suitable for 
refilling the trench until the same shall have been refilled. 

Paragraph 14. Pumping and Bailing. —The contractor 
shall furnish all necessary machinery for the work, shall 
pump, bail, or otherwise remove any water which may be 
found or shall accumulate in the trenches, and shall perform 
all work necessary to keep them clear of water while the 
foundations and the masonry are being constructed or the 
sewer laid. In no case, unless by special permission of the 


200 


SEWERAGE. 


engineer, shall water be allowed to run over the invert or 
foundation or through the sewer until the cement is satisfac¬ 
torily hardened. The disposal of the water after removal 
shall be satisfactory to the engineer. 

Paragraph 15. Shoring and Sheathing. — Whenever 
necessary the sides of the trench shall be braced and rendered 
secure and either open or close sheathing used, to the satis¬ 
faction of the engineer; such sheathing and bracing to be left 
in until the trench is refilled, all such bracing and sheathing 
being done at the contractor’s expense. Sheathing left in 
permanently by the order of the engineer, and only such, will 
be paid for at the price bid. When left in the trench sheath¬ 
ing shall be cut off at a point about 1 foot below the surface. 
The contractor shall, at his own expense, shore up and other¬ 
wise protect any building which may, in the opinion of the 
engineer, be endangered by the work. 

Paragraph 16. Railway-crossings. —When any railway¬ 
lines are to be crossed or interfered with specific directions 
as to the time and manner of doing this work will be given by 
the engineer, and the contractor shall conform to such direc¬ 
tions. He shall be allowed for material furnished and made 
part of the permanent construction, so far as it may be addi¬ 
tional to that indicated on the plan, but all other work shall 
be done at his own cost. 

Paragraph 17. Interference with Existing Structures 
and Watercourses. —In excavating and back-filling trenches 
and laying the sewer care must be taken not to move or injure 
any gas-, water-, sewer-, or other pipes, conduits, or structures 
without the order of the engineer. If necessary the contractor 
shall, at his own expense, sling, shore up, and secure, and 
maintain a continuous flow in said structures, and shall repair 
any damage done to them and keep them in repair until the 
final acceptance of the completed works, leaving them in as 
good condition as when uncovered. Should it be necessary 


SPECIFICATIONS , CONTRACT , ESTIMATE OF COST. 201 

to move the position of a pipe or conduit this shall be done 
in accordance with the instructions of the engineer, and the 
contractor shall be allowed for material furnished and made 
part of the permanent construction, so far as it may be addi¬ 
tional to that indicated upon the plans, and for labor per¬ 
formed on such additional construction, but all other work 
shall be done at his own expense. 

At such street-crossings and other points as may be 
directed by the engineer the trenches shall be bridged in a 
secure manner, so as to prevent any serious interruption of 
travel upon the roadway and sidewalks and also to afford 
necessary access to public and private premises. The mate¬ 
rial used and mode of constructing such bridges and the 
approaches thereto must be satisfactory to the engineer; the 
cost of all such work must be included in the regular price bid 
for the sewer. ( Crossings should not be tunnelled under , since 
it is almost impossible to so refill the tunnels as to prevent after- 
settlement , but should be bridged. Direct access to the street 
should be given to fire-engme houses and usually to livery- 
stables.') All fire-hydrants shall be left uncovered and accessi¬ 
ble. The contractor shall at his own expense provide for all 
watercourses, gutters, and drains interrupted by the work, 
and replace them in as good condition as he found them. 

Paragraph 18. Rock Trenches. —When the excavation 
for a pipe sewer or drain is made through rock or other 
material too hard to be readily or conveniently removed for 
admitting the hubs of the pipe the trench shall be excavated 
at least 4 inches deeper than the grade of the outside bottom 
of the pipe and [filled with concrete up to and around such 
pipe, as shown upon the plans] [refilled to such grade with 
sand or loam, free from stones or other hard substances, 
thoroughly rammed]. When rock is encountered in the 
trench it shall be stripped of earth and the engineer notified 
and given proper time to measure the same before blasting. 


202 


SEWERAGE. 


All rock removed which has not been measured by the 
engineer will not be estimated as rock excavation. Measure¬ 
ment for rock excavation will be limited to 6 inches on either 
side of the sewer, and trench-slopes of 8 vertical to I hori¬ 
zontal. In all cases of blasting the blast shall be carefully 
covered with heavy timbers chained together, and the engineer 
may limit the number of simultaneous discharges. Not more 
than 30 pounds of dynamite shall be kept on hand at one time 
in any one place. No blasting shall be done within 40 feet 
of the finished sewer or 10 feet of an uncovered gas- or 
water-pipe, and the end of the finished sewer shall be covered 
or stopped with plank or earth during each blast. (If the 
sewer-end is not so protected there is a possibility of stones flying 
into the sewer and also of the concussion of air opening the 
joint si) 


Art. 53. Construction. 

Paragraph 19. Foundations. — When timber or pile 
foundations other than those shown in the plans are neces¬ 
sary, in the opinion of the engineer, special designs will be 
furnished the contractor, who, in accordance with such 
designs, shall place such foundations in position satisfactory 
to the engineer. Planking in platforms shall be laid in the 
manner directed, closely joined, and each plank spiked to each 
cap or sill with nails or spikes of a length at least 2 \ times the 
thickness of the plank. If cradles or platforms are laid 
directly upon the ground this must be graded perfectly even 
and smooth to receive them and give a good and firm bearing 
throughout. If caps or sills are used the spaces between them 
and under the planking must be filled with good earth 
thoroughly rammed. 

Where piles are used they shall be driven to refusal, unless 
extending more than 10 feet below the foundation, when they 


SPECIFICATIONS , CONTRACT , ESTIMATE OF COST . 203 

shall show a penetration in inches under the final blow not 

1 w h 

greater than -1, in which L is the weight to be borne 

by each pile, w is the weight of the hammer in pounds, and 
h its fall in feet. After driving, the piles shall be sawed off 
truly and evenly at the proper elevation for receiving the 
caps, which shall be fastened to them with i-inch drift-bolts 
of a length twice the depth of the sill, holes for such bolts 
having first been bored with a $-inch bit. If any pile shall 
be out of line more than J the diameter of its upper end the 
engineer may refuse to estimate it and may order another 
driven in its place. 

Concrete or stone-masonry foundations shall be con¬ 
structed where ordered in a manner similar to that specified 
for “ Concrete ” and 1 ‘ Stone Masonry.” 

Paragraph 20. Concrete. —Concrete, unless otherwise 
specified, shall be composed of 1 part by bulk of natural 
cement, 3 parts of sand, and 5 parts of broken stone, gravel, 
or furnace-slag of approved quality, free from dust and dirt 
and broken so as to pass in every way through a 2-inch ring. 
All material shall be actually measured for each batch, the 
cement compacted in barrels as received (or, if received in 
bags, an equivalent quantity as ascertained by trial), the sand 
and stone in similar barrels or specially prepared boxes. In 
mixing, the sand shall be spread out upon a suitable platform 
or box and the cement deposited upon this; these shall then 
be thoroughly mixed dry until the whole is of an even, 
uniform color, when sufficient clean water shall be added to 
form a thick paste. The stone, which has previously been 
thoroughly wet, shall then be added and the whole shall be 
quickly and thoroughly mixed, until every stone is coated 
with mortar, water being gradually added by sprinkling, if 
necessary, to obtain a better consistency. If mixing be done 
by machinery it shall produce a mixture equally as good as by 



204 


SEWERAGE. 


the above method. Concrete must not be mixed in quantities 

greater than required for immediate use, and any which has 

begun to set shall not be retempered or used in any way. 

Concrete shall be deposited in layers not to exceed 9 inches 

in thickness, and settled by thorough light ramming, sufficient 

to bring water to the surface. One course shall follow another 

as rapidly as possible. Where fresh concrete is to be placed 

in contact with that already set or partly set all loose stone 

or concrete not thoroughly compacted shall be removed from 

the surface of the latter, which shall be washed clean of all 

dirt and given a thin coat of mortar. If such a surface be 

hard set it shall previously be thoroughly water-soaked. 

When concrete is in place all wheeling, working, or walking 

on it must be prevented until it is firmly set, and until such 

time it shall be kept damp and protected from the sun. 

* 

Such forms and centres as may be necessary to give the 
finished concrete the desired form shall be furnished by the 
contractor without extra charge. These shall be sufficiently 
stiff and substantial to retain the concrete firmly in place, and 
shall not be withdrawn until the same has set to the satisfac 
tion of the engineer. No concrete shall be made or used 
when the temperature is below 35 0 Fahr. without the permis¬ 
sion of the engineer, whose instructions and restrictions for 
such use shall be followed. ( When an entire sewer is composed 
of concrete a better quality , generally made of Portland cement, 
is used for the invert, and the inside is plastered.) 

Paragraph 21. Stone and Brick Masonry. —Stone and 
brick masonry, unless otherwise specified, shall be laid with 
mortar composed of 1 part by measure of natural cement to 
2 of sand, mixed as specified for concrete mortar. No mortar 
shall be used after it has set or partially set. 

Stone masonry must be laid true and by line and built of 
the exact dimensions shown in the plans of the work. All 
stones shall be laid upon their natural beds and roughly 


SPECIFICATIONS, CON TP ACT, ESTIMATE OF COST. 20 5 

squared on the joints, beds, and faces, the stone breaking 
joints at least 6 inches, and with at least one header for every 
three stretchers. Headers shall be at least 3 feet long or 
extend entirely through the wall. No stone once bedded 
shall be lifted by spalling, but any spalls used must be em¬ 
bedded in the mortar before setting the stone. Each stone 
shall be floated to place in a full bed of mortar and every 
joint thoroughly filled with the same. No dressing of stone 
upon the wall will be allowed. {For river- or retaining-walls 
further specifications should be added as to thickness of joints, 
character of face dressing, etc.) 

For brick masonry in straight walls or sewers none but 
whole, sound brick shall be used. For manholes, flush-tanks, 
and similar work a limited number of half brick may be used, 
not to exceed -J- of the whole in any case. Unless the engineer 
direct otherwise each brick shall be thoroughly wetted imme¬ 
diately before being laid. {If the brick absorbs practically no 
water this wetting should be omitted, as likely to cause the brick 
to slide on the mortar and cause uneven work.) It shall be laid 
with a full, close joint of cement mortar on its bed, ends, and 
side at one operation. In no case is mortar to be slushed in 
afterward. Special care shall be taken to make the face of 
the brick-work smooth, and all joints on the interior of a 
sewer shall be carefully struck with the point of a trowel or 
pointed to the satisfaction of the engineer. Where pipe- 
connections enter a sewer or manhole “ bull’s-eyes ” shall be 
constructed by laying rowlock courses of brick around them, 
the cost of such construction being included in the regular 
price bid for the sewer or appurtenance. Around pipe more 
than 15 inches in diameter 2 rowlock courses shall be laid. 

Brick-work in sewers shall be laid by line, each course 
perfectly straight and parallel to the axis of the sewer. Joints 
appearing in the sewer shall in no case exceed i inch in width. 
Sewers shall conform accurately in section and dimensions to 


206 


SEWERAGE. 


the plans of the same. All inverts and bottom curves shall 
be worked from templets accurately set, the arches are to be 
formed upon strong centres accurately and solidly set, and the 
crowns keyed in full joints of mortar. No centres shall be 
drawn until the arch masonry has set to the satisfaction of the 
engineer and refilling progressed up to the crown. They 
shall be drawn with care, so as not to crack or injure the work. 
The extrados is to be neatly plastered with cement mortar \ 
inch thick, the arches being cleaned and wetted just before 
plastering. The end of each section of brick sewer shall be 
toothed or racked back, and before beginning the succeeding 
section all loose brick at the end shall be removed and 
the toothing cleaned of mortar. All brick-work shall be 
thoroughly bonded, adjacent courses breaking joints at least 
J the exposed length of the brick. 

Stone blocks shall be laid in Portland-cement mortar com¬ 
posed of equal parts by measure of cement and sand. Joints 
shall not exceed f inch in width. The face of the masonry 
shall be such that there shall be no projection beyond the 
general surface exceeding £■ inch. All joints shall be cleaned 
out to a depth of \ inch and pointed with neat Portland- 
cement mortar. All stone-block work shall be laid in other 
respects as specified for brick-work. 

If there should be any distortion of the sewer before 
acceptance this shall be corrected by tearing down and rebuild¬ 
ing. No local patching will be allowed, but when repairs are 
necessary a section shall be removed at least 3 feet long and 
including the entire arch, or the entire sewer if the defect is 
in the invert. Leakage of ground-water into the sewer shall 
be similarly corrected, unless it can be prevented by calking 
the joints with oakum saturated in cement, with wooden 
plugs, or other material acceptable to the engineer. 

Paragraph 22. Laying Pipe Sewers.—Previous to being 
lowered into the trench each pipe shall be carefully inspected, 


> 


SPECIFICATIONS , CONTRACT , ESTIMATE OF COST. 20J 

and those not meeting the foregoing specifications shall be 
rejected, and either destroyed or removed from the work 
within io hours; except that pipe suitable for sub-drains may 
be used for that purpose, but shall be kept apart from the 
sewer-pipe. All lumps or excrescences on the ends of each 
pipe shall be removed before it is lowered into the trench. 
No pipe shall be laid except in the presence of the engineer 
or his authorized inspector, and the engineer may order the 
removal and relaying of any pipe not so laid. The trench 
shall be excavated in accordance with Paragraphs 13 and 18. 
No sewers shall be laid within 10 feet of the excavating or 40 
feet of the blasting. Pipes having any defects which do not 
cause their rejection shall be so laid as to bring these in the 
top half of the sewer, and if the bell or spigot be broken the 
defective place must be liberally covered with neat-cement 
mortar, reinforced with a piece of pipe or pipe-ring if the 
engineer so direct. 

The pipes and specials shall be so laid in the trench that 
after the sewer is completed the interior surface thereof shall 
conform accurately to the grades and alignment fixed and 
given by the engineer. All adjustment to line and grade of 
pipes laid directly upon the bottom must be done by scraping 
away or filling in the earth under the body of the pipe, and 
not by blocking or wedging up. Before laying, the interior 
of the bell shall be carefully wiped smooth and clean, and the 
annular space shall be free from dirt, stones, or water. [(For 
hub-and-spigot joints.) A narrow gasket of packing dipped in 
cement grout shall be properly calked into each joint, after 
which cement mortar shall be introduced therein. Such 

gasket shall be in one piece, of sufficient length to reach 

« 

entirely around the pipe and of a thickness sufficient to bring 
the bottoms of the two pipes to the same level. No joint 
shall be cemented until the gaskets of the next two joints in 
advance are properly inserted. Special care must be taken 


208 


SE WEE A GE. 


to properly fill with mortar the annular space at the bottom 
and sides as well as at the top of the joints. After such 
space has been filled, the cement having been compacted with 
a wooden or iron calking-tool, a neat finish shall be given to 
the joint by the further application of similar mortar to the 
face of the hub so as to form a continuous and even bevelled 
surface from the exterior of said hub to the exterior of the 
spigot all around.] [(For bevelled joints.) The bevels shall 
each be covered with a layer of cement at least £ inch thick 
and the spigot pipe steadily pushed home with some force. 
A band of cement at least £ inch thick and 3 inches wide shall 
then be neatly wiped around the outside of the sewer at the 
joint.] All water must be kept out of the bell-hole during 
laying, or else such bell-hole must be completely filled out 
with the cement mortar specified or with concrete, for which 
mortar or concrete no extra compensation will be allowed. 
The interior of the joint shall be wiped clean of cement by a 
wad made of a sack filled with hay, large- enough to tightly 
fill the pipe and attached to a rod or cord, which shall at all 
times be kept in the sewer and pulled ahead past each joint 
as soon as it is cemented. The mortar used shall be com¬ 
posed of [1 part cement to 1 of sand] [neat cement] wet to a 
thick paste. ( Engineers do not agree as to the advisability of 
using neat-cement mortar. Experiment seems to show that 
natural cement gives a tighter joint if mixed with sand , Port¬ 
land if used neat.) Natural cement shall be used under 
ordinary conditions, but the engineer may require the use of 
quick-setting or of Portland cement when he thinks it neces¬ 
sary. 

As soon as the cementing of any joint has been completed 
the bell-hole under the hub must be carefully and compactly 
filled with sand, loam, or fine earth, so as to hold the external 
mortar finish of said joint securely in its place. Refilling 
shall also be made with selected material, free from stones, 




SPECIFICATIONS, CONTRACT , ESTIMATE OF COST. 20g 

carried halfway up the sides or circumference of the entire 
length of pipe and compacted with a proper tamping-tool. 
The trench shall then be filled to a point at least 2 feet above 
the top of the pipe with material containing no stone larger 
than 2 inches in any dimension. 

While the pipes and specials are being laid in each section 
between manholes or other permanent openings light from the 
remote end of the section shall remain constantly in plain view 
throughout the entire length of such section or division. 
Section: between openings will in general not exceed 300 to 
400 feet; in particular cases the distance may be somewhat 
greater. 

At such places as will be directed by the engineer, 
branches will be inserted in the sewer for future connections. 
Each branch thus inserted shall be closed by a thin vitrified 
stoneware cover or plug, which shall be placed before the 
special pipe is lowered into the trench. The covers shall be 
so inserted and cemented in as to prevent any water entering 
the sewer, at any time before their removal, through such 
branches. The entire cost of furnishing and setting such 
covers shall be included in the regular price bid for branches. 
Where directed by the engineer deep cut connections (Fig. 

- - -) shall be constructed as shown upon the plans. 

Any omission of the required branches, manholes, lamp- 
holes, or other special constructions indicated upon the plans, 
or that may be specially ordered beforehand by the engineer, 
shall be corrected by the contractor at his own expense. 

Before leaving the work for the night or at any other time 
the end of the sewer shall be securely closed with a tight- 
fitting plug. 

Paragraph 23. Laying Sub-drains.—Sub-drains shall be 
laid in sub-trenches excavated of the dimensions and in the 
location shown upon the plans, and of such depth as is neces¬ 
sary to lay the pipe at the grade given by the engineer. This 


210 


SEWERAGE. 


sub-trench shall be filled with clean broken stone or gravel, 
not less than J inch nor more than i inch in any dimension, 
up to the drain invert; this broken stone or gravel being laid 
in by hand or shovels and lightly compacted, so that there 
may be no future settlement. On this the drain-pipe shall be 
laid accurately to grade, having first been inspected and all 
pipe not meeting the specifications having been rejected. A 
piece of cheese-cloth or similar material satisfactory to the 
engineer, at least 5 inches wide and twice as long as the out¬ 
side circumference of the pipe, shall be laid on the broken 
stone with its centre under the joint between two pipes; first 
one end and then the other of this shall be carried over the 
pipes and under the opposite side, care being taken to keep 
the cloth spread out and its centre over the joint. The pipes 
shall be separated by a space of about \ inch. The space 
between the pipes and the sides of the sub-trench shall then 
be carefully filled with broken stone or gravel as specified 
above, carefully compacted, which material shall be similarly 
placed to a depth of 6 inches above the pipe. Where directed 
by the engineer this stone-filling shall be covered by hemlock 
plank, to be paid for as “ timber in foundations.” If any 
earth or other material shall fall into the sub-trench while the 
laying of stone filling is proceeding, such material and the 
adjacent stone-filling shall be removed and clean stone be put 
in its place. 

Where directed by the engineer branches shall be inserted 
in the sub-drain for future connections. These shall be closed 
as specified for sewer branches, and the specification as to the 
omission of sewer specials shall apply to sub-drain specials 
also. 

Paragraph 24. Regular Appurtenances.—Manholes of 

the various kinds—line, intersection, drop, etc.-—lamp-holes, 
flush-tanks, inlets, and other appurtenances shall be built 
where the engineer may direct, in size, form, thickness, and 


SPECIFICATIONS, CONTE ACT, ESTIMATE OF COST . 211 

all other respects in accordance with the plans, but manholes 
whose height exceeds 12 feet shall have walls 12 inches thick 
below that depth. All appurtenances shall be brought up 
accurately to the grade given by the engineer. Great care 
shall be taken to make the channels in manholes and lamp- 
holes conform accurately to the sewer grade. In the case of 
pipe-sewers split pipe shall be used for the inverts to these 
channels where possible. Where a curve in the channel or 
some other condition prevents this the channel shall be formed 
of bricks on edge, set in Portland-cement mortar. Brick 
channels shall be lined with neat Portland-cement mortar \ 
inch thick, and the inverts shall be exactly semi-circular of the 
diameter of the pipes which they connect. If these be of 
different diameters the channel shall taper uniformly from one 
size to the other. 

Flush-tanks and inlets shall be plastered on the outside 
with \ inch of cement mortar; and on the inside shall be given 
three coats of thin Portland-cement grout, without sand, 
applied with a brush, each coat being allowed to set before 
the next is applied. ( This will be more certain to make a 
water-tight construction than plaster mg with mortar.) 

Care shall be taken to place the inlet tops, when these are 
in the sidewalk, exactly in line with the curb, and to place 
the bottoms of the openings or the gratings exactly on the 
gutter grade given. 

All manholes and flush-tanks shall be fitted with steps 
similar to those shown on the plans, and spaced 15 inches 
r\part vertically. All tops or other fittings shall be set during 
the construction or at the completion of each appurtenance, 
in a firm, neat, and workmanlike manner. 

All concrete, stone, or brick masonry shall conform to the 
specifications given in Paragraphs 20 and 21. Each appurte¬ 
nance shall be begun within 24 hours of the time it is reached 


212 


SE WEE A GE. 


in the laying of the sewer, and shall be completed and the 
excavation closed as expeditiously as possible. 

Art. 54. Back-filling and Cleaning Up. 

Paragraph 25. a. Back-filling. —In back-filling sewer- 
trenches loose, fine earth, free from stones, shall be used up 
to a point 2 feet above the sewer, and shall be thoroughly 
compacted in 6-inch layers with hand-rammers. The re¬ 
mainder of the trench shall contain not more than J broken 
rock, and no stone of this shall weigh more than 50 pounds. 
If necessary to meet this requirement the contractor shall 
supply suitable material for back-filling. The filling of the 
trench above the level of 2 feet above the sewer shall be 
rammed in 9-inch layers, or, when directed by the engineer, 
the trenches shall be water-tamped. Water-tamping shall be 
done in each case as directed by the engineer. All back-fill¬ 
ing shall be done by hand and in no case shall scrapers or 
ploughs be used. In back-filling of tunnels or under railroad 
tracks especial care shall be taken to thoroughly compact the 
material. ( The question of back-filling is a very troublesome 
one . In most soils, when the diameter of the sewer does not 
exceed one sixth of the depth of the trench , all the earth 
excavated can be returned without leaving any ridge and with¬ 
out any appreciable after-settleme7it. But this can be done only 
at cc nsiderable expe?ise—from 4 to 12 cents for each cubic yard 
of back-filling—by careful ramming or water-tamping; in tough 
clay no way has yet been found to accomplish this. When the 
trench is through fields or unpaved streets this extra payment is 
not generally warranted by the benefits derived; but through 
paved streets it generally is. The above specifications are 
similar to those ordinarily used, but contractors generally 
understand that they will not be enforced except in well-paved 
streets, and bid accordingly. It is preferable to leave the option 


SPECIFICATIONS, CONTRACT , ESTIMATE OF COST. 213 

confessedly with the engineer as to whether the trench shall be 
tamped , and pay for the tamping which is ordered , having it 
well done. The following specification is offered as a substitute , 
to be rigidly enforced .) 

Paragraph 25. b. Back-filling.—In back-filling sewer- 
trenches loose, fine earth, free from stones, shall be used up to 
a point 2 feet above the sewer, and shall be thoroughly com¬ 
pacted in 4-inch layers by hand-rammers, there being two 
rammers to each shoveller. Rammers for this purpose shall 
weigh from 4 to 6 pounds each, and have not to exceed 10 
square inches of face. The remainder of the trench shall 
contain not more than one third broken rock, and no stone of 
this shall weigh more than 50 pounds. If necessary to meet 
this requirement the contractor shall supply suitable material 
for back-filling. Unless otherwise specified the trench above 
the level of 2 feet above the sewer shall be filled by hand with 
this material up to within 1 foot of the surface, and the 
remainder of the filling shall be made of fine material contain¬ 
ing no stone having any dimension greater than 2 inches. 
The filling shall be crowned above the trench, having a height 
above the street surface of twice as many inches as the top 
width of the trench in feet, and neatly rounded off, the paving 
material previously removed, if any, being spread evenly over 
the top. After refilling, and for 6 months after the comple¬ 
tion of this contract, the contractor shall from time to time 
refill any settlements which may occur, constantly maintaining 
the trench in a neat and safe condition, and deliver it over in 
that condition at the end of that time. Hand-ramming or 
water-tamping shall be used where directed, and as follows, 
an additional sum being paid therefor according to the price 
bid. 

For hand-ramming the earth shall be spread by shovels in 
4-inch horizontal layers and solidly compacted with rammers 
weighing from 6 to 8 pounds and having a face of not to 


214 


SEWERAGE. 


exceed 20 square inches. There shall be two rammers to 
every shoveller, and the former shall be of at least as great 
strength and efficiency as the latter. The paving shall be 
restored in as good condition as found, being given a crown 
of \ inch over the trench, but not, in the case of macadam or 
gravel paving, overlapping the old paving. During back¬ 
filling no sheathing which is to be drawn shall at any time 
extend into earth which is being rammed, but it shall be 
drawn so as to be always above it, if it cannot be at once 
entirely removed. 

For water-tamping the earth shall be levelled off in hori¬ 
zontal layers 2 feet thick and flooded with water until, after 
standing for 5 minutes, water shall just show on the surface, 
when another layer shall be thrown in and flooded. This 
shall be continued up to within 2 feet of the surface and 
allowed to stand for a few hours. The last 2 feet shall then 
be put in and hand-rammed as specified above, and the paving 
relaid. 

No water shall be turned into the trench until all cement- 
work in sewers and appurtenances shall have had full time to 
set. 

If a trench is rammed or water-tamped any earth which 
may have slipped or caved from the bank shall be thrown out 
of the trench and the space refilled and tamped in the same 
way as the trench proper, without extra compensation. 

Paragraph 26. Street Surfaces. —In all paved, macada¬ 
mized, or improved streets generally the surface of the 
trenches shall be finished without needless delay, in the most 
workmanlike manner, with the same kind of roadway im¬ 
provement that was removed in excavating the trench, and 
so that the underlying courses, as well as the finished surface, 
shall conform to the remainder of the roadway, and shall in 
every respect be equal in quality, character, materials, and 
workmanship to the street improvement existing over the line 


SPECIFICATIONS , CONTRACT , ESTIMATE OF COST. 21 5 

of the trench immediately previous to making the excavation. 
The expense of restoring the pavement or improvement must 
be included in the price per lineal foot of sewer. 

Paragraph 27. Cleaning up. —As soon as the trench has 
been refilled and paving replaced all stones, plank, or other 
refuse material of whatever description deposited and left by 
the contractor on the streets shall be removed therefrom and 
the said streets restored in all respects to the same condition 
as before the trenching was commenced. All surplus earth 
which may be left on the street after the trenches have been 
refilled as specified above shall be regarded as the property of 
the contractor, and must be removed as soon as possible at 
his expense. 

Paragraph 28. Final Inspection. —Upon notification by 
the contractor of the completion of the work herein contracted 
tor the engineer will carefully inspect all sewers, appurte¬ 
nances, and all other work done by the contractor. In each 
stretch of pipe sewer intended to be straight light shall be 
visible from one end to the other. Any broken or cracked 
pipe shall be replaced with sound ones. The interior of brick 
sewers shall be of the required shape and dimensions, sound 
and of a uniform surface. Any deposits found in the sewers, 
protruding cement or packing, shall be removed and the sewer- 
bore left clean and free through its entire length. There 
shall be no appreciable amount of leakage into any stretch of 
sewer. All underdrains shall discharge water freely and give 
evidence of having a clean and open bore. All manholes, 
lamp-holes, and other appurtenances shall be of the specified 
size and form and of a neat appearance, and their tops shall 
be set to the proper grade. In general the work shall comply 
with these specifications, and if found not to do so in any 
respect shall be brought to the proper condition by cleaning, 
pointing, or, if necessary, excavating, and rebuilding, all at 
the expense of the contractor. But if it be found after 


216 


SE WEE A GE. 


uncovering any pipe or other work at the order of the 
engineer that no defect exists, or that the defect was not due 
to any fault of the contractor, then the expense of this shall 
be borne by the city. 

Art. 55. General Provisions, Payments, etc. 

Paragraph 29. General Provisions. —If any alterations 
in plan directed by the engineer diminish the quantity of 
work to be done they shall not constitute a claim for damages 
nor for anticipated profits, and any increase or decrease shall 
be paid for or deducted according to the quantity actually 
done, and at the price established for such work under this 
contract. 

The work shall be prosecuted in such manner and from as 
many different points, at such times and with such force as 
the engineer may, from time to time during the progress of 
the work, determine. 

The contractor will be furnished with a set of drawings 
showing the details and dimensions necessary to carry out the 
work, dimensions in figures thereon having precedence over 
the scale. These plans and a copy of these specifications are 
to be kept constantly at the work by the contractor or his 
authorized foreman. The plans submitted to contractors for 
proposals are to be interpreted in conjunction with the speci¬ 
fications, and descriptions of the character of the work appear¬ 
ing on the plans are made a part of these specifications. No 
deviations from the drawings will be allowed without the 
direction of the engineer to that effect. 

Should it be necessary at any time to move monument- 
stones or other permanent records the contractor shall not 
disturb them until given permission by the engineer. 

The contractor shall provide suitable stakes, plank, and 
forms, and render such assistance to the engineer, at his own 


SPECIFICATIONS , CONTRACT , ESTIMATE OF COST. 21J 

expense, as may be necessary to establish lines and grades for 
the guidance of his work, and shall carefully preserve said 
points at all times. 

If any person employed by the contractor on this work 
shall appear to be incompetent or disorderly he shall be dis¬ 
charged immediately on the requisition of the engineer, and 
such person shall not again be employed on the work. 

Paragraph 30. Responsibility for Injuries. —The con¬ 
tractor shall be responsible for injuries to person and property 
inflicted during the prosecution of the work, and for all 
damages caused by the negligence of the contractor or any of 
his employees, workmen, or servants, and the city may at its 
discretion withhold the amount of such injury or damage from 
any estimate due him which may be needed to make good 
such damages or injuries, and the city shall not in any wise 
be liable therefor. 

The contractor shall place sufficient lights on or near the 
work and keep them burning from twilight to sunrise, shall 
erect suitable railing or protection about the open trenches, 
and provide all necessary watchmen on the work by day or 
night, for the safety of the public. 

Paragraph 31. Imperfect Work. —When any work or 
material is found to be imperfect, whether passed upon or not 
by the inspector, the said work shall be taken up and replaced 
by new work at any time prior to final acceptance. 

If the contractor shall be notified by the engineer of any 
requirements or precautions neglected or omitted, or of any 
work improperly constructed, he shall at once remedy the 
same, and if he fail so to do the engineer, under the direction 

1 

of the city, shall perform such work at the contractor’s 
expense and deduct the same from amounts due or to become 
due the contractor. 

Paragraph 32. Unnecessary Delays. —In case of any 
unnecessary delay, in the opinion of the engineer, he shall 


218 


SEIVEEA GE. 


notify the contractor in writing to that effect. If the con¬ 
tractor should not, within 5 days thereafter, take such 
measures as will, in the judgment of the engineer, insure the 
satisfactory completion of the work the engineer may then, 
under authority from the city, notify the aforesaid contractor 
to discontinue all work under this contract, and it is hereby 
agreed that the contractor is to immediately respect said 
notice and stop work and cease to have any rights to posses¬ 
sion of the ground. The engineer shall thereupon have the 
power to place such and so many persons as he may deem 
advisable, by contract or otherwise, to work at and complete 
the work herein described, and to use such materials as he 
shall find upon the line of said work, or to procure other 
materials for the completion of the same, and to charge the 
expense of said labor and materials to the aforesaid contrac¬ 
tor; and the expense so charged shall be deducted and paid 
by the party of the first part out of such money as may be 
then due, or at any time thereafter become due, to said con¬ 
tractor under and by virtue of this agreement or any part 
thereof; and in case such expense is less than the sum which 
would have been payable under this contract if the same had 
been completed by the party of the second part [he] [they] 
shall be entitled to receive the difference, and in case such 
expense is greater the party of the second part shall pay the 
amount of such excess so due. 

Paragraph 33. Extra Work. —If any work of the general 
nature of the work herein contracted for, but for doing which 
a bid has not been especially made, shall need to be done the 
contractor shall do the same under the direction of the 
engineer, and shall receive therefor the actual cost of labor 
and material used plus ten per cent (10#) for superintendence 
and use of tools, but he shall not be entitled to receive pay¬ 
ment for any work as extra work unless ordered by the 
engineer to do the same as such. No claim for extra work 


SPECIFICATIONS , CONTRACT\ ESTIMATE OF COST. 219 

will be allowed if not made before the payment of the next 
following monthly estimate. 

Paragraph 34. Time of Commencement and Completion. 

—The party of the second part agrees to begin the work 
herein contracted for within two weeks of the awarding of the 
contract, and to fully complete the work herein specified on 

or before the.day after the awarding of said contract, 

but the party of the first part may extend the time of com¬ 
pletion should they deem it for the best interest of the city. 
[It is expressly- understood that the party of the second part 
agrees to pay all expenses, such as engineering and inspec¬ 
tion, that the city may be put to by reason of the work being 
incompleted at the time specified in the contract.] [For each 
day after the time specified that the contract remains un¬ 
completed $2 5 will be deducted from the amount due the 
contractor, and for each day by which the contract is com¬ 
pleted previous to the time specified the contractor shall be 
entitled to a bonus of $25.] [For each day after the time 
specified that the contract remains uncompleted $25 will 
be deducted from the amount due the contractor, and it 
is hereby expressly understood that said sum shall be deemed 
and taken in all courts to be the liquidated damages for the 
non-performance of the work in the manner aforesaid, and not 
in the nature of a penalty.] 

Paragraph 35. Definitions. —Whenever the word “ en¬ 
gineer ” is used in the specifications it refers to the engineer 
in charge of the work and also to his authorized agents. 

The ** party of the first part ” is the city by and for which 
the work herein described and referred to is being done, and 
the “ party of the second part ” is the person or persons con¬ 
tracting to do said work. 

The word “ sewer ’ ’ in its general sense in these specifica¬ 
tions refers to the sewer-barrel and to any bends, slants, 
branches, or other details joined to or forming a part thereof. 


220 


SE WEE A GE. 


The word “appurtenance” refers to all manholes, lamp- 
holes, flush-tanks, inlets, and all structures forming a part of 
the sewerage system, but not included in the term “ sewer.” 

Paragraph 36. Position of the Engineer. —The engineer 
shall have the final decision on all matters of dispute involving 
the character of the work, the compensation to be made 
therefor, or any question arising under this contract. He 
shall, as representing the city, have the option of making any 
changes in the line, grade, plan, form, position, dimensions, 
or material of the work herein contemplated, either before or 
after construction is begun, and all explanations or directions 
necessary for carrying out and completing satisfactorily the 
different descriptions of work contemplated and provided for 
under this contract will be given by said engineer. 

Paragraph 37. Duties of the Contractor. —The contrac¬ 
tor must perform the work contracted for strictly according to 
these specifications, and follow at all times, without delay, all 
orders and instructions of the engineer in the prosecution and 
completion of the work and every part thereof, and constantly 
be on the ground or be represented by a duly qualified person 
to look after the work and receive instructions. 

Paragraph 38. Measurements and Payments. —Meas¬ 
urements of sewers and drains shall be taken from the centre 
of the uppermost manhole or flush-tank on each line to the 
centre of the manhole at its junction with a main or lateral, 
or to the centre line of such main or lateral at the junction, 
including all branches, manholes, or other appurtenances 
along the line. The depth by which sewer prices will be 
graded will be measured from the surface of the ground to the 
under side of the sewer-pipe or masonry or of the timber 
platforms or foundation-sills. The price bid for sewers or 
drains shall include furnishing all material and labor for 
excavating, shoring, constructing the sewer or drain in 
accordance with the specifications and plans, back-filling, 


SPECIFICATIONS , CONTRACT , ESTIMATE OF COST. 221 

restoring the street-surface as previously specified, and for all 
matters in connection therewith heretofore specified as being 
so included. Measurements of connections shall be taken 
from the outside (bell) end of the branch to the upper end of 
the connection-pipe. Branches shall be paid for by the piece 
at the price bid, which shall include the cost of furnishing and 
fixing plugs in said branches where necessary. 

Deep-cut connections shall be paid for at the prices bid 
for “deep-cut connections,” “pipe,” “concrete,” and 
“ timber in foundations,” according to the actual quantities 
used, the bid for “deep-cut connections” including the 
combining of these and the setting of, and extra care in back¬ 
filling around, the pipe. 

Flush-tanks shall be paid for at the price bid for each par¬ 
ticular size of tank, this to include the tank complete as set 
forth in the drawings and specifications, including the excava¬ 
tion and back-filling, ventilation-pipe and iron head. 

Ordinary manholes and lamp-holes shall be paid for on the 
basis of a depth of 8 feet, with an additional amount for each 
foot by which the depth exceeds 8 feet, the price bid to 
include excavating and back-filling, furnishing and setting iron 
castings and steps, and completing the whole as set forth in 
the plans and specifications. The depth of flush-tanks, man¬ 
holes, and lamp-holes shall be measured from the invert of a 
pipe sewer, or the springing of a brick sewer, to the top of 
the iron head when properly set. 

The price bid for“ crossing-” and “ drop-manholes ” shall 
be an additional sum over and above the bid for the same as 
a regular manhole, and shall be held to cover furnishing 
material for and constructing the crossing or drop device as 
shown in the plans, as an addition to the regular manhole. 
The bid for the crossing-manhole shall be a lump sum; that 
for the drop-manhole shall be per vertical foot, measuring 
from the invert of the lower to that of the upper sewer. 


222 


SE WEE A GE. 


The price bid for inlets, catch-basins, and other appurte¬ 
nances shall include the excavation and back-filling, and fur¬ 
nishing all materials and constructing each appurtenance in 
strict conformity to the plans and specifications. 

The price bid for stone paving shall be per square foot, 
and shall be over and above the price for the sewer or man¬ 
hole in which it is laid. 

The price for stone, brick, or concrete masonry not other¬ 
wise provided for shall be per cubic yard by actual measure¬ 
ment in place, provided such dimensions do not exceed those 
indicated or implied in the plans or instructions of the 
engineer. 

Iron-work, both cast and wrought, shall be paid for by the 
pound, but no payment for iron-work as such shall be made 
for the heads or steps or other devices included in the man¬ 
holes and other appurtenances as shown in the plans and speci¬ 
fications. Cast-iron pipe will be paid for at the price per foot 
bid for the same. 

The price for timber in foundations shall include the fur¬ 
nishing and setting of the same. The price bid for furnishing 
piles shall be for the lengths actually delivered, where these 
do not exceed those ordered by the engineer. The price for 
driving piles shall be per foot, measured from the bottom of 
the pile when driven to the surface of the ground in which it 
is driven, and shall include cutting off the piles at the eleva¬ 
tion given by the engineer. 

The price bid for tamping trenches shall be by the cubic 
yard of trench above a point 2 feet above the top of the 
sewer, the bottom width heretofore specified being allowed 
and side slopes of I in 15 in earth and 1 in 8 in rock. 

The engineer on the first of each month, or within 5 days 
thereafter, during construction, will estimate approximately 










SPECIFICATIONS, CONTE ACT, ESTIMATE OF COST. 223 

the amount of work completed during the preceding month, 
according to these specifications, and eighty-five per cent 
{85$) of the amount due beyond the reservations herein made 
will be paid the contractor on or before the 15th day of each 
month for the work of the preceding month. 

When the contract shall have been completely performed 
on the part of the contractor the engineer shall proceed to 
make final measurements and estimates of the same, and shall 

certify the same to the city .. who shall, except for 

cause herein specified, pay to the contractor, on or before the 
15th day after such completion of the contract, the balance 
which shall be found due, excepting therefrom such sum as 
may be lawfully retained under any provision of this contract. 

Art. 56. Contract. 

Accompanying the specifications and bound with them should 
be the contract proper , of which a form is given : 

This Agreement, made and concluded the. 


day of.in the year One Thousand Eight Hundred 

and.. by and between the City of.. 


of the first part, and.. Contractor, of the 

second part, 

WITNESSETH, That the said party of the second part (has) 
(have) agreed, and by these presents (does) (do) agree with 
the said party of the first part, for the considerations herein 
mentioned and contained, and under the penalty expressed 
in a bond bearing even date with these presents and hereto 
attached, to furnish at (his) (their) own proper cost and 
expense all the necessary material and labor, except as herein 
specially provided, and to excavate for and build, in a good, 
firm, and substantial manner, the sewers indicated on the 
plans now on file in the office of the city engineer, and the 








224 


SEWERAGE. 


connections and appurtenances of every kind complete, of the 
dimensions, in the manner, and under the conditions herein 
specified; and (has) (have) further agreed that the engineer in 
charge of the work shall be and is hereby authorized to 
inspect or cause to be inspected the materials to be furnished 
and the work to be done under this agreement, and to see 
that the same correspond with the specifications. 

The party of the second part hereby further agrees that 
(he) (they) will furnish the city with satisfactory evidence that 
all persons who have done work or furnished material under 
this agreement, and are entitled to a lien therefor under any 

law of the State of.. have been fully paid or are 

no longer entitled to such lien, and in case such evidence be 
not furnished as aforesaid such amount as the party of the 
first part may consider necessary to meet the lawful claims of 
the persons aforesaid shall be retained from the moneys due 
the said party of the second part, under this agreement, until 
the liabilities aforesaid may be fully discharged and the evi¬ 
dence thereof furnished. 

The said party of the second part further agrees that (he) 
(they) will execute a bond in a sum equal to 25 per cent of 
the contract price, secured by a responsible Indemnity of 
Guarantee Company of, or authorized by law to do business 

in, the State of. and satisfactory to the city, or by 

at least three responsible freeholders of.County 

satisfactory to the city, for the faithful performance of this 
contract, conditioned to indemnify and save harmless the said 
city, its officers or agents, from all suits or actions of every 
name or description brought against any of them for or on 
account of any injuries or damages received or sustained by 
any party or parties, by or from the said party of the second 
part, (his) (their) servants or agents, in the construction of 
said work, or by or in consequence of any negligence in guard¬ 
ing the same or any improper materials used in its construe- 





SPECIFICATIONS , CONTRACT , ESTIMATE OF COST. 22$ 

tion, or by or on account of any act or omission of the said 
party of the second part, or (his) (their) agents, in the per¬ 
formance of this agreement and for the faithful performance 
of this contract in all respects by the party of the second part; 
and the said party of the second part hereby further agrees 
that so much of the moneys due to (him) (them), under and 
by virtue of this agreement, as shall be considered necessary 
by the said city may be retained by the said party of the first 
part, until all such suits or claims for damages as aforesaid 
shall have been settled and evidence to that effect furnished 
to the satisfaction of said city. 

The said party of the first part hereby agrees to pay, 
and the said party of the second part agrees to receive, 
the following prices as full compensation tor furnishing all 
materials, labor, and tools used in building and constructing, 
excavating and back-filling, and in all respects completing the 
aforesaid work and appurtenances, in the manner and under 
the conditions before specified, and as full compensation for 
all loss or damages arising out of the nature of the work afore¬ 
said, or from the action of the elements or from any unfore¬ 
seen obstructions or difficulties which may be encountered in 
the prosecution of the same, and for all expenses incurred by 
or in consequence of the suspension or discontinuance of the 
said work, and for well and faithfully completing the same and 
the whole thereof according to the specifications and require¬ 
ments of the engineer under them, to wit: 

(.Insert here spaces for making bids , being careful to include 
every item for which bids are invited . As an example:} 

For all 36-inch brick sewer, trenches 

from 6 to 8 feet deep. $-per lineal foot 

For water-tamping. .per cubic yard 

For each manhole 8 feet deep, complete - 

For each vertical foot of manhole more 

than 8 feet deep, 8-inch wall. . 









226 


SE WEE A GE. 


For each vertical foot of manhole more 

than 8 feet deep, 12-inch wall. . 

For timber foundations. .per M B. M. 

etc. etc. 

And the said party of the second part further agrees that 
(he) (they) will not assign, transfer, or sublet the aforesaid 
work, or any part thereof without the written consent of the 
city, and that any assignment, transfer, or subletting without 
the written consent aforesaid shall in every case be absolutely 
void. 

In Witness whereof the said party of the second part 
(has) (have) hereunto set (his) (their) hand and seal and the 
said party of the first part has caused these presents to be 

sealed with its common seal and to be signed by the. 

.on the day and year above written. 

It is recommended that the engineer refer to Johnson’s 
“ Contracts and Specifications,” where will be found a full 
discussion of the subject from both the legal and engineering 
standpoint. 


Art. 57. Estimate of Cost. 

It is generally desirable, and frequently required by law, 
that a careful estimate be made of the cost of the work to be 
done. For this purpose map, plans, specifications, and profile 
should be carefully studied to obtain quantities, and the 
amount of rock to be excavated, quicksand, and ground-water 
ascertained, and in general as careful a study made of the 
conditions as a contractor would make before bidding. Also 
the prices of materials should be obtained, including the cost 
of getting them upon the ground, and from these as close an 
estimate made as possible of the actual cost of constructing 
the system. To this-should be added io to ioo per cent for 









SPECIFICATIONS. CONTRACT, ESTIMATE OF COST. 227 

profit and contingencies, the latter amount when the work is 
to be done under great risks and subject to possible losses. 

Out of a dozen bids made on one sewer contract there are 
generally one or two quite low, two or three others quite high, 
and the remainder more or less close together midway between 
these, and usually representing a fair price for the work, which 
also the engineer’s estimate should do. The estimate should 
not be too low, as this often gives rise to suspicion of inten¬ 
tional deception, and if made the basis of an appropriation of 
funds for construction may lead to a forced curtailment of the 
amount of work done. On the other hand, an unduly high 
estimate may discourage any appropriation whatever. Prob¬ 
ably no act of the sewerage engineer is more readily appre¬ 
ciated by the public at large than the making of an estimate 
closely approximating the actual cost. 

The cost of brick, lumber, and sand varies with each 
locality and should be obtained from local dealers. That of 
cement and pipe varies little except with the freight, and this 
variation is slight between different places in the same section 
and on main freight-lines. 

A schedule price has been adopted by all sewer-pipe 
makers, from which large discounts are allowed. Such a list 
is given below. The discount allowed contractors for car-load 
lots at present (1902) near New York City is about 70 to 72 
per cent for sizes under 24 inches. 

Table No. 17. 

LIST PRICES OF VITRIFIED CLAY SEWER-PIPE, AND WEIGHTS OF 

STANDARD PIPE. 


Size, inches... 

2 

3 

4 

5 

6 

8 

9 

IO 

12 

*5 

18 

20 

24 

Straight pipe, per foot.. 

0.14 

0.16 

0.20 

0.25 

0.30 

0.45 

o .55 

0.65 

0.85 

1.25 

I . 70 

2.25 

3-25 


O. 40 

0.50 

0.65 

0.85 

I . IO 

1.80 

2.25 

2.75 

3 - 5 ° 

4-75 

6.50 

7-50 

II .OO 

Branches, 2 feet long, each.... 

0.63 

0.72 

0.9a 

113 

I »35 

2.03 

2.48 

2-93 

3-83 

5- 6 3 

7-65 

10.13 

14.63 

Traps, each. 

I .OO 

1.50 

2.00 

2.50 

3 - 5 ° 

5 - 5 ° 

6.50 

7.50 

10.00 

.... 

. . . 

. 

. . . 

Weight of straight pipes per 







26 


45 

63 

84 

98 


foot, pounds. 

6 

7 

10 

12 

16 

22 

32 

130 


Slants are charged 50 per cent more than plain pipe, and 








































228 


SE WEE A GE. 


measured on the long side of the slant, but none less than 12 
inches long. 

Each additional branch or trap is charged branch price. 

Double-strength pipe is allowed io per cent less discount 
than standard pipe. 

Increasers are pipe with the hub on the small end and 
reducers with the hub on the large end, and are charged 
double the price of 2 feet of pipe of the size of the large end. 

Channel or split pipe, which is pipe cut in two or more 
pieces lengthwise, costs the price of whole pipe. 

Stoppers or plugs for closing pipe cost ■§■ as much as I foot 
of pipe of the size in which they are used. 

Table No. 18 . 


LIST PRICES OF DRAIN-TILE. 


Sjze, inches. 

2 

2 i 
.015 


4 

c 

6 

8 

10 

Price, straight pipe. 

.012 

J 

.020 

.030 

J 

.040 

•055 

.080 

.140 


36- and 38-inch WOODEN-STAVE PIPE in Los Angeles, 
Cal., cost $2.25 to $2.50 per foot, complete.* 

Light-weight CAST-IRON PIPE, first quality, cost in 1902 
about as follows: 

Table No. 19 . 


COST OF LIGHT IRON PIPE. 


Size, 

inches... 

4 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

27 1 30 

33 

Cost 

per foot.. 

•30 

.40 

•52 

•77 

.96 

1.10 

1.30 

1.50 

2.00 

2.25 

2-75 

3-103.75 

4.15 


One barrel of cement, used neat, should lay the following 
lengths of sewer, pipes 3 feet long: 

Table No. 20 . 


LENGTHS OF PIPE SEWER ONE BARREL OF CEMENT WILL LAY. 


Size, inches... 

4 

6 

8 

9 

10 

12 

15 

18 

20 

24 

Length, feet.. 

500 

350 

200 

175 

150 

100 

75 

65 

60 

50 


The following gives approximately the lowest practicable 
cost of excavating trenches in compact loam or material 


* See also “Water-supply Engineering," page 448 . 











































SPECIFICATIONS , CONTRACT, ESTIMATE OF COST. 22 g 

excavated with equal ease. The prices for shoring and 
sheathing are to be added where necessary. These are based 
on continuous work with gangs of the most economical size. 
House-connections or other short lines would cost more. 
Profit is not included. Trench machines excavate at a cost 
of 12 to 18 cents per cu. yd., plus $175 to $400 per month 
rental. 

Table No. 21 . 


COST OF EXCAVATING AND BACK-FILLING AND OF SHEATHING ; 

DOLLARS PER LINEAL FOOT. 

(Compact Loam ; No Ground-water ; No Machinery.) 


Depth of trench, feet . 

6 

8 

IO 

12 


l6 

18 

20 

4- to 10-inch sewer. 

•075 

. IO 

.14 

.20 

•25 

•33 

•39 

• 52 

15-inch sewer. 

.09 

.125 

•175 

.24 

•315 

•39 

• 49 

.65 

20 “ “ . 

.105 

•15 

.21 

.29 

• 38 

.465 

.585 

.78 

24 “ “ . 

.12 

•175 

•245 

• 34 

•45 

• 545 

.685 

.91 

30 “ “ . 

.14 

.20 

.28 

•39 

•50 

.62 

• 78 

1.04 

Close j Lumber, @ $10. 

•34 

.42 

•51 

.64 

.80 

.92 

1.06 

1.22 

sheathing. ( Setting. 

.08 

.09 

.11 

• 13 

.20 

.22 

•24 

.26 

If used 2 5 times *. 

.22 

.26 

•32 

•38 

•50 

.58 

.66 

•75 

If sheathing-planks 4 feet apart 

. 10 

.12 

•15 

.18 

.24 

•27 

•30 

•33 


* j- used the second time, l the third time, £ the fourth time. With care good sheathing 
may be used an average of five times. 


Quicksand may cost from two to ten times the above. 
No estimate can be given for it. ROCK EXCAVATION in sewer- 
trenches usually costs from 75 cents to $2 per cubic yard. 
The greater the amount of rock per running foot to be 
excavated the more cheaply it can be done. 

The approximate cost of laying sewer-pipe, including all 
but the excavation, is given in the following table: 


Table No. 22 . 

COST OF LAYING SEWER-PIPE, CENTS PER LINEAL FOOT. 



2 -f 00 t 

Lengths. 





3 

foot Lengths. 





Size, inches. 

4 

5 

6 

8 

9 

IO 

12 

15 

18 

20 

24 

27 

30 

33 

36 

Unloading, hauling, 
and distributing.* 

0.15 

0.18 

0.21 

0-35 

0.38 

0,41 

0.63 

0.90 

1.20 

1.50 

2.10 

3.0° 

4.00 

4.46 

5-25 

Laying, cost of jute, 
calking. 

1.23 

1.38 

i -55 

1.62 

1.78 

1.97 

2 . 3 1 

2.58 

3.00 

3 - 7 ° 

4 - 5 ° 

5.06 

5-48 

6.00 

6.80 

Cement, mixed ... 

0.44 

O.5O 

0-55 

0.58 

0.65 

o -75 

o -93 

I . II 

1.32 

t -55 

2.00 

2.35 

2.90 

3.86 

4-57 

T otal.. 

1.82 

2.06 

2.31 

2-55 

2.81 

3-!3 

3 -87 

4-59 

5-52 

6-75 

8.60 

IO.4I 

12 38 

14.32 

16.62 


* Teams hauling 4500 pounds per load; average haul one mile; $3.50 per day. 


































































230 


SEWERAGE. 


The approximate cost of building circular brick sewers is 
given in the following table. This does not include excava¬ 
tion or back-filling. 


Table No. 23 . 

COST OF CIRCULAR BRICK SEWERS PER LINEAL FOOT. 



One Ring. 

Two Rings. 

Three Rings. 

Interior Diameter, Feet. 

2 

3 

3 

4 

5 

5 

6 

Brick, @ $8 per M. 

.40 

•58 

I -31 

1 • 7 1 

2.10 

3-36 

3-95 

Mixed j Cement, @ 80 cts. per bbl.. 

.075 

. 11 

.23 

.29 

.36 

.58 

•70 

1:2 ( Sand. 50 cts. per yd. 

.015 

.02 

.04 

.05 

.07 

. II 

• 13 

Masons, @ $2.50. 

. 10 

. 14 

•30 

• 37 

•45 

.72 

.92 

Helpers, @ $1.50. 

.15 

.22 

• 45 

.58 

.70 

I.08 

1.43 

Total.. 

• 74 

1.07 

2-33 

3.00 

3-68 

5.85 

7 -i 3 


The approximate cost of manholes, 3 feet by 4 feet 6 
inches on the bottom, is given in the following table. A 
4-foot circular manhole will cost about 4 per cent more. This 
table does not include the cost of the iron-work. The brick¬ 
work is taken as 8 inches thick down to a depth of 12 feet, 
and below this as 12 inches thick. 


Table No. 24 . 

COST OF MANHOLES, 3 FT. X 4 FT. 6 IN. 
(Brick 2 in. X 4 in. X 8 in.; i-inch joints.) 


Depth, top of Brick-work to sewer-invert. 

8 ft. 

10 ft. 

12 ft. 

14 ft. 

16 ft. 

18 ft. 

20 ft. 

Brick, $8 per M. 

IO.36 

I 2./0 

15.04 

19.00 

23.25 

26.75 

30-15 

Mixed j Cement, @ 80 cts. per bbl... 

I .48 

I . 82 

2.15 

2.72 

3-32 

3.82 

4.31 

1:2 ] Sand, 50 cts. per yd. 

. 26 

•33 

.38 

•49 

• 58 

.68 

•75 

Masons, @ $2 =,0.. 

2.00 

2.25 

2.90 

3-50 

4-45 

5-15 

5-75 

Helpers, @ $1.50. 

2.40 

2.70 

3-48 

4.20 

5-35 

5-50 

6 00 

Total. 

16.50 

19.80 

23-95 

29.91 

3>-95 

41.90 46.96 


Foundations of concrete 6 inches thick, with benches for 8-i nch pipe $3.25 

Cast-iron tops and covers, 450 to 800 lbs., @ to 2 cts. $5.6 o-$i6.oo 

Steps, wrought-iron, each. 20 cts. 


Cast-iron tops and covers, 450 to 800 lbs., @ i]- to 2 cts. $5.6 o-$i6.oo 

Steps, wrought-iron, each. 20 cts. 


In the above tables labor is taken at $1.50 per day, teams 
at $3.50. The cost given does not include superintendence, 
use of tools, profit, or any of the general expenses of manage- 






















































SPECIFICATIONS , CON TP ACT, ESTIMATE OF COST. 23 I 

ment, but is thought to be liberal, and sufficient to include 
these under good management. 

Natural CEMENT can be had in the Eastern States at from 
65 cents up, Portland from $1.80 up, per barrel in car-load lots. 

The cost of SAND will vary with the locality from 25 cents 
to $2 per cubic yard. 


Art. 58. Methods of Assessment. 

While not an engineering feature of sewer construction, 
the methods employed in paying for a system may be briefly 
considered to advantage. In many cases the city pays for 
the construction and later reimburses itself by special assess¬ 
ments on benefited property or by annual rental; in some 
the entire cost is borne by the city at large; in others part is 
borne by the city, part by the property-owners. The city’s 
payment may be made from the ordinary funds or by issuing 
sewerage bonds. In Philadelphia, Pa., the assessment bills 
are assigned to the contractor, with right of lien for collection. 

Probably no better general statement of sewer-assessment 
methods in this country could be given than by quoting from 
an article on the “ Theory and Practice of Special Assess¬ 
ments,” by J. L. Van Ornum in volume XXXVIII of the 
Transactions of the American Society of Civil Engineers 
(September, 1897): 

“In a majority of cases the city pays for main sewers, 
either wholly or all above the usual assessment for a branch 
sewer. A large number also assess this expense by the area 
method upon the property affected, either entirely or all 
exceeding the usual charge for a lateral, as before. Less 
commonly a percentage is assessed and the city pays the 
balance, or the cost is divided between an area and a frontage, 
charge, or other plans are followed in its distribution. Of the 


232 


SE WEE A GE. 


inethods pursued in providing for the collecting system, con¬ 
sisting of the laterals or branch sewers, a plurality prefer to 
charge the cost upon abutting property according to the 
frontage rule; though nearly an equal number have an arbi¬ 
trary rate per foot front, varying from 30 cents to $2, the city 
to pay the balance; and a considerable number assess the cost 
either upon the drainage-district or upon a zone of a certain 
width on each side of the sewer, in the ratio that the area of 
the lot or land in question bears to the total assessed area, 
streets being excluded. Of the remaining methods some 
■divide the expense between the city and private property by 
various processes, others charge it upon property by a com¬ 
bination of the frontage and area rules, and sometimes the 
city bears the whole cost. 

“ The frequently occurring plan of assessing upon contigu¬ 
ous property the equivalent expense of a sewer of small size, 
where a large sewer is placed, is commendable. This method 
would obviously have no advantage where the total cost of 
both mains and branches are together distributed pro rata 
upon all the property benefited, nor any application where 
the city pays entirely for its sewer system; but where 
adjacent property is charged with a certain part or all the 
expense of the sewer, inequality would result if the method 
just indicated, or an equivalent specified fixed charge not 
depending on the size of pipe, is not applied. Necessarily 
the larger sewers are laid on the lower ground, where, except 
manufactoi ies and similar industries, the less valuable and 
productive property occurs. Here, also, are more generally 
found tenements and the habitations of laboring men who are 
less able to meet the burden, while the commercial districts, 
and especially the dwellings of the more prosperous, are in 
the higher portions of the city, where the sewers are naturally 
of smaller size. The latter classes of citizens make the greater 
use of sewers, and it would manifestly be unjust to fail not 


SPECIFICATIONS , CON TP ACT, ESTIMATE OF COST. 233 

only to lay upon them an equal burden, but to charge them 
even a smaller amount than the average. The cost of appur¬ 
tenances, like manholes, lamp-holes, catch-basins, and flush¬ 
ing-tanks, is sometimes met by the city and sometimes 
included in the cost of the sewer and so distributed. The 
disposition of these expenses depends upon the provisions of 
law. House-connections with the sewer are made at the 
expense of the property. In addition a few cities impose a 
special charge for the privilege of connection for the purpose 
of increasing the sewerage fund of the city, but this is to be 
deprecated as tending to discourage the general use of the 
sewers, which has become a sanitary necessity in cities. 

“ The question of the distribution of the cost of a sewer 
system is also a complicated one, whether considered in the 
light of practice or principle. All the city has an interest, 
both general and sanitary, in its sewers, and the property- 
owners have a direct interest as abutters as well as a particu¬ 
lar, but more general, one in the larger mains of their district 
sewers. As far as the trunk sewers are concerned, their con¬ 
struction is of more general import to the city as a whole than 
to any individual users, and their cost might well be paid by 
general taxation. Whether or not the city’s share in building 
sewers should always be devoted to these mains, because they 
have the least direct connection with property, may be 
uncertain, as custom or local usage may dictate the assump¬ 
tion of the cost of work on street intersections or in front of 
city lots, parks, and other property, or other expenses, 
besides the occasional defaults that come upon the city, all of 
which would probably equal the proportion suggested. All 
the reasons already given for considering it equitable for the 
city to share in the expense of its water-works system apply 
equally to its sewer system; where there are no storm-water 
sewers (a separate system) for which the city usually pays, it 
is but just that the city should aid in the construction of the 


234 


SE WEE A GE. 


more usual combined system, which has to receive the storm¬ 
water from the streets. It would be unfair to expect lots or 
lands so distant that they may not be able for years to secure 
connection with the system as it develops to contribute much 
toward paying for trunk sewers which will at best be of only 
indirect special advantage to them ; and it is believed that the 
city assuming a share, to the extent of 20 or 30 per cent of 
the cost of its sewer system, would furnish but a fair equiva¬ 
lent for its benefit, and make less burdensome the individual 

assessments which so frequently cause objection and retard 

/ , 

the construction of these necessary improvements. 

“ Of the methods followed perhaps the most adequate 
plan of dealing with the portion of the expense of sewers that 
is to be assessed is that common one of considering together 
all the sewers of each sewer district and distributing the cost 
over the district in proportion to the advantage received. In 
many cities this allotment is attempted by the frontage rule, 
but deep lots generally have a larger share in the use of 
sewers than have shallow ones of the same frontage. The 
amount of storm-water to be removed from lots is far from 
having a definite relation to frontage, and other irregularities 
result. Other cities apportion this assessment by the area 
rule, but of equal areas that which has the greater frontage 
enjoys conditions favoring a larger number of buildings or 
other improvements which imply a greater interest in the 
sewer system, and therefore should furnish a correspondingly 
larger contribution; and as systems are often built a portion 
at a time, lands remote from the constructed portions should 
not be required to pay equally with lots that are enabled to 
make use of them at once. 

“ In consequence of the inequitable features inhering in 
both systems, in numerous instances it has become an im¬ 
proved method to combine the two processes and assess 40 per 
cent, more or less, by frontage and the balance by the area 


SPECIFICATIONS , CON TP ACT, ESTIMATE OF COST. 235 

rule, or to apply some equivalent procedure that will effect a 
similar combination of methods. This system of apportion¬ 
ment is growing in favor. It corrects the more serious errors 
of either method used alone. It is not complex in applica¬ 
tion, and in principle it is as definite and as easily understood 
by the people affected as either single process. Probably no 
more adequate plan for sewer assessments has been exten¬ 
sively used than, after the city has contributed its due por¬ 
tion, assessing by frontage an amount equal to the cost of a 
smaller size of pipe upon abutting property, as previously 
mentioned, or an equivalent amount, and distributing the 
remainder in proportion to area. 

“ In some Massachusetts cities the plan has recently been 
applied of partly paying the cost of the sewer system and its 
maintenance by a sewer rental corresponding in its principle 
to the water rates of water-works systems. The private con¬ 
tribution to sewerage construction should correspond very 
closely to the use made of them; and to effect this Brockton 
and other Massachusetts towns have adopted the plan of such 
an annual charge depending upon the amount of water used, 
claiming that the quantity of sewage to be disposed of can be 
approximately estimated by reference to the water rate. If 
this plan does not tend to discourage the use of sewers, if it 
does not too much complicate the system of assessment and 
proves otherwise practicable, it may furnish a valuable addi¬ 
tion to the methods of apportionment. Its practical opera¬ 
tion will be watched with interest by those making a study of 
special assessments.” 

Since the assessment is strictly a legal function, the State 
laws and city charter will to some extent control the methods 
in each particular case. For instance, in New Jersey assess- 

V 

ment by the front foot has been decided illegal. It is prob¬ 
able that in all States it is legal to assess in proportion to 
benefits received, and this too would seem to be demanded 


236 


SEWERAGE. 

by fairness. These benefits consist of: (1) removal of house- 
sewage from the buildings; (2) removal of rain-water from 
premises and streets (where combined or storm sewers are 
built); (3) draining the land when wet; (4) increasing the 
value of property; (5) a general public benefit to the entire 
city, whether it is all sewered or not, consequent on the im¬ 
proved healthfulness of certain sections, on increased valua¬ 
tion and therefore reduced tax rates, and on the recommen¬ 
dation to prospective residents that it “ has sewers.” The 
1st, 3d, and 4th are individual benefits, the 2d a combination 
of individual and general, the 5th a general one. It would 
appear, therefore, that a perfectly just apportionment of the 
cost would assess part, but only a part, of this upon property 
directly benefited, and this at fixed rates in proportion to 
front foot and area combined, with an additional charge for 
each connection made or an annual rental in lieu thereof. 
This charge may be collected either as an assessment, to be 
paid at once or to bear interest and be apportioned into sev¬ 
eral annual payments; or in the form of rentals, at fixed rates 
for the different classes of sewage-contributors or else propor¬ 
tioned to some function of the water-consumption. The 
method employed at Malden, Mass., of giving each property- 
holder the option of either of these methods has some advan¬ 
tages. It is in most cases desirable to make each assessment 
or rental operative as soon as it becomes possible to connect 
the property with the sewer and make use thereof, as tend¬ 
ing to hasten the general use of the system. Whatever the 
method it should be simple of application and readily under¬ 
stood, should not be burdensome to the poorer property- 
holders, and should encourage early and general use of the 
sewers. 

For descriptions of various methods employed see the 
paper quoted from above, Report of the Engineer to the 
Brockton Sewerage Commission, and Journal of the Associa¬ 
tion of Engineering Societies for January and March, 1897. 


PART II. 


CONSTRUCTION. 


CHAPTER X. 

PREPARING FOR CONSTRUCTION. , 

Art. 59. Contract Work or Day Labor. 

There are two general plans by which a city or town may 
construct a sewerage system, viz., by contract or by day 
labor. In a majority of instances, probably a very large one, 
the contract method is adopted, but in quite a number the 
work is done under the general charge of the city engineer or 
a special agent or committee who purchases material, employs 
labor, and looks after the work generally. If the work can be 
kept entirely free from politics and conducted without “ fear 
or favor ” by a good manager experienced in this line of work 
the latter method will probably be the more economical for 
the city and give the more satisfactory results. Unfortu¬ 
nately these conditions exist in few cities or towns, and the 
contract method is usually the cheaper one, and frequently 
gives better results than construction by home labor under 
foremen too often unskilled in sewerage-work. There may 
be cases where, even with and in spite of the existence of the 
above objections, construction directly by the city is prefer¬ 
able. For instance, the work may be of an uncertain nature. 


p 


237 



238 


SE WEE A GE. 


its details difficult to foresee and set forth in a contract; or it 
may be unusually hazardous, causing contractors to add ioo 
or even 200 per cent to the estimated cost to balance the risk, 
which risk the city might think it better to assume itself. In 
some instances villages have undertaken sewerage-work as a 
means of giving employment in unusually hard times to 
citizens, who would thus be enabled to pay part of their wages 
back to the treasury in taxes, and also relieve the poorhouse 
of a large number of possible inmates. 

Since, however, sewerage-work is generally done by con¬ 
tract, the succeeding chapters will be made applicable particu¬ 
larly to construction by this method. But the matter is 
equally applicable to work done by the city or its immediate 
agent, which agent should conduct the work as the contractor 
would have been compelled to conduct it. 

It may be sometimes advisable for the city to purchase 
the materials and contract for the labor of construction. In 
this way the quality of the materials is under the immediate 
control of the city. In the matter of cost there is usually 
very little difference one way or the other, unless it be that 
the city is charged a little more, owing to a “ commission ’ * 
which must be paid to certain officials who control the award¬ 
ing of the contracts for material. It is an excellent plan for 
the city to furnish cement, sand, and pipe, and see that there 
is no unnecessary waste of these. There is then no tempta¬ 
tion for the contractor to use defective material or too little 
cement. 

Systems have been built by letting the contract for exca¬ 
vation to one party, and that for pipe-laying and brick-work 
to others, the material being purchased by the city. This is 
almost sure to work unfavorably to the city and give rise to 
the greatest confusion, of responsibilities if not of work. 


PREPARING FOR CONSTRUCTION. 


239 


Art. 60. Obtaining Bids. 

If work is to be let by contract the probabilities are that 
the greater the number of bidders the lower will be the sum 
for which the work can be constructed, a partial cause of this 
being the lessened liability of collusion between the bidders. 
To reach contractors two methods are open: to send notice to 
individual contractors, or to advertise in such a way and place 
as will attract the attention of a large number. Each method 
has its advantages, and perhaps a combination of the two 
might give the best results. But it is probable that one or 
two advertisements judiciously placed will reach all who would 
be reached by the first method, and many others besides. 
For a small village the best advertising medium is the con¬ 
tractors’ journal having the widest circulation in that part of 
the country, which is also true for a city if the work amounts 
to more than a very few thousand dollars. For small con¬ 
tracts in cities having several capable contractors among its 
citizens the local paper will perhaps give sufficient publicity 
to the desire for bids, but village papers are generally useless 
for this purpose. For contracts of $5000 or more an adver¬ 
tisement in one or two prominent engineering and contracting 
papers will usually pay for itself many times over. 

The customary method of bidding is to have each con¬ 
tractor submit a sealed proposition, all of these being opened 
at a time fixed beforehand. It would be unfair, if not illegal, 
to open any sealed bid before this time or to receive another 
bid after any had been opened. To satisfy both the public 
and the contractors of the honesty and fairness of the award¬ 
ing of the contract it is customary to open the bids and read 
them aloud at a meeting open to the public, or at least to all 
bidders and to newspaper representatives. The opportunities 
for dishonesty are so great if the bids are opened in secret or 


240 


SE WEE A GE. 


one received after others have been read that regard for their 
own reputations usually influences the officials making the 
award to adopt the above methods. 

That there may be no informal or incomplete bids it is 
desirable that all bids be made on forms furnished by the city 
and accompanied by copies of the specifications and contract 
similarly furnished. It would be possible for a bidder whose 
bid had been accepted to refuse to contract for the work 
unless he were bound in some way. For this reason it is well 
to require that each bid be accompanied by a certified check, 
to be returned to the bidder unless he refuse to sign the con¬ 
tract based upon his bid, if so requested. 

The laws of different States and cities differ as to the lati¬ 
tude given in awarding contracts. In some the contract must 
be awarded to the “ lowest bidder,” in others to the “ lowest 
responsible bidder,” while in still others there is no restric¬ 
tion. Justice to the taxpayers and fairness to the bidders 
will usually dictate awarding to the lowest bidder, unless 
there be reason to think that he will be unable, through 
inexperience, to do creditable work, or that, his bid being 
lower than the work can probably be done for, he will later 
abandon the work, and the consequent delay and legal com¬ 
plications, even though his bond insure the ultimate comple¬ 
tion of the contract, will be detrimental to the city’s interests.. 
If it becomes evident during construction that the contractor 
cannot but lose money there is usually a tendency to favor 
him in minor matters, to grant him extensions of time and 
aid him in other ways which detract more or less from the 
excellence of the work. In order to avoid, on the other hand, 
the necessity of awarding the contract to a too high bidder 
when there are no reasonably low ones the city should 
“ reserve the right to reject any or all bids.” 


PREPARING FOR CONSTRUCTION . 


24I 


Art. 61. Engineering Work Preliminary to 

Construction. 

As soon as possible after the signing of the contract the 
contractor should submit samples of the material he wishes 
to use, and these should be carefully examined by the 
engineer, and if accepted should be retained and marked for 
future identification and compared from time to time with 
the material actually furnished. 

The contractor should be notified some days in advance 
of the point or points at which he is to begin work. Reason¬ 
able deference should be made to his wishes in this matter, 
since it is his privilege and duty to so organize the work as to 
secure the greatest efficiency at the least cost to himself. If, 
for instance, part of the work lies through wet ground and 
sub-drains are to be used it is ordinarily to his interest, and 
indirectly to the city’s also, that the work begin at an outlet 
to which all ground-water will drain, or at a point at which a 
pump, once set up, can drain the work for long distances 
without moving its location, as at the junction of two mains. 
It is also usually desired by the contractor that, if two or 
three gangs are to work at as many places, they may be 
within a few blocks of each other for convenience of oversight. 
It will ordinarily be to the interests of both contractor and 
city to work in as dry ground as possible, and hence to leave 
until summer droughts construction through low, soggy land. 
Construction across or near streams should not be carried on 
when there is a possibility of floods or freshets, if it can be 
avoided. Both trench- and masonry-work should be avoided 
in winter weather if possible, for it is then costly to the con¬ 
tractor, and it is impossible to be sure that the mortar is 
uninjured, or to restore the streets to good condition with 
frozen earth. 


242 


SE WERA GE. 


Ordinarily the contractor will desire to place upon the 
street, along the line of the work, pipe, brick, sand, lumber, 
etCo This cannot be denied him, but he should be compelled 
to place and pile this material so as to interfere with travel as 
little as possible, and along only those stretches of street in 
which construction is to be begun within a week, or ten days 
at the outside. This material should be inspected as it is 
delivered, and that condemned removed at once. 

Just before the work begins it is well to run levels care¬ 
fully over all bench-marks to see that they have not been 
disturbed and to check previous levelling; also to establish 
new ones if necessary. .It is desirable to so place these that 
one of them can be seen from the instrument when set up for 
giving grades to any part of the work. They should be 
accurate within at least .003 of a foot. 

Art. 62 . Other Preliminaries. 

Final arrangements should now be made for the oversight 
of the work, the proper instruments obtained, engineering and 
inspecting assistants engaged, an office or other headquarters 
arranged for, notebooks and blanks obtained for making and 
preserving records, final arrangements made as to right of way 
across private property and along county roads or others not 
controlled by the city or village. Arrangements should be 
made also for locating the branches for house-connections at 
the points desired by the property-owners. For this purpose 
it is well to publish in the paper or otherwise make known to 
the citizens that each is desired to drive, at his fence-line or 
curb, a stake indicating the point at which he wishes his 
house-connection to enter his property, and that in case no 
such stake is driven the engineer or inspector will use his 
judgment in locating such branches. Another method is that 
of requesting that sketches of the property showing such 


PREPARING FOR CONSTRUCTION. 


243 


point be handed in on blanks to be furnished by the engineer; 
but the inability or hesitancy of many citizens to make the 
simplest drawing is an objection to this plan. 

Counsel for the city should pass upon the sufficiency and 
correctness of the contracts signed, of the bonds given and of 
their signers, and all other legal matters in connection there¬ 
with, before the contractor is permitted to begin work. 


CHAPTER XI. 


LAYING OUT THE WORK. 

Art. 63 . Lining Out Trenches. 

SINCE the trench is seldom more than 6 inches wider on 
each side at the bottom than the sewer to be placed in it, it 
is necessary that the trench itself be carefully aligned, and 
this cannot be entrusted to the contractor except for short 
distances. For giving him the line the safest plan is to drive 
stakes or spikes along the centre of the proposed trench at 
intervals of about 50 feet. To assist in finding these, for 
checking, and to locate the centre of the sewer during con¬ 
struction, the distance should be taken from each of these to 
the curbing opposite, if there is any, or to a reference-stake, 
and a note made of this. The centre spikes or stakes should 
be some uniform distance apart to facilitate finding them. 
They should be set by a transit placed over the centre of a 
manhole on the line. The line should of course be straight 
between manholes, except in the case of large sewers, which 
may be curved, in which case the centre stakes should be set 
10 or 15 feet apart. The location of manholes, flush-tanks, 
etc., should be fixed by two or more reference-stakes and 
pointed out to the contractor before he begins excavating, 
that he may make allowance for them in sheathing. 

Some engineers in giving line rely entirely upon reference- 
stakes placed a uniform distance from the centre of the trench, 


244 


LAYING OUT THE WORK. 


245 


because the centre stakes will be removed in excavating. An 
experience with the unreliability of contractors’ tapes and 
foremen’s intelligence seems to argue in favor of the centre 
stakes, however. 

It is well to do a large part of this lining out before con¬ 
struction gets well under way, since it is probable that the 
engineer corps will be kept busy with other work later. Each 
line should be located only after due consideration of the 
points referred to in Art. 34. 

Art. 64 . Giving Grade. 

Several methods of giving grade are employed by different 
engineers, the principal being: By means of a cord stretched 
over the centre of the trench and parallel to the sewer grade; 
by stakes driven to grade along the centre line in the bottom 
of the trench; and by stakes driven at the ground-surface near 
the edge of the trench, their tops a uniform or stated distance 
above the sewer grade. (The grade used in both designing 
and construction is that of the inside bottom of the invert, 
which for convenience will be called the invert.) Each of 
these is used for both pipe and brick sewers, but only the first 
method is at all adapted to accurate laying of pipe sewers. 
For brick sewers either method may be used, but the first is 
most convenient in that the invert-templet can be set at any 
point along the trench, and that the bottom of the trench can 
be carried to the exact grade at every point, in advance of 
setting the templet, by measuring down from the cord. If 
stakes are driven in the bottom the templets can be accurately 
set only at points close to these, and the stakes can be driven 
only when the bottom is within a foot or less of grade, which 
necessitates the presence of the engineer upon the work 
almost constantly. If the stakes are driven along the edge of 


246 


SEWERAGE. 


the trench they can be set even before the excavation has 
been begun, enough for several days in advance being set at 
one time; but it is almost impossible to avoid errors in 
measuring down from these, since they are not directly above 
the sewer, and the stakes are apt to become loose or fall out 
with the cracking and caving of the edge of the trench. 

The cord used in the first method may be fastened to a 
strip of wood nailed in a vertical position to a plank which 
stands upon edge with one end resting upon the ground on 
each side of the trench. This plank should extend at least 18 
inches or 2 feet beyond the trench on each side and be firmly 
bedded into solid ground so that it cannot possibly settle, and 
should be held upright on edge by a stake driven on each side 
at each end, or by stones and earth solidly banked around the 
ends. These grade-planks should be not more than 33^ feet 



Fig. 5.—Method of Setting Grade-plank. 


apart—25 feet would perhaps be better, since the cord will sag 
too much if the distance between supports be greater. On 
the top edge of these planks the centre of the trench is 
marked, and strips of wood about 1 inch X 2 inches X 24 
inches are nailed so that one edge of each is in this centre line 
and truly vertical, as determined by a plumb-bob. On this 
edge is placed a mark exactly a whole number of feet above 
the sewer-invert immediately beneath, and a slight notch is 
cut to receive the cord. All notches in a given length of 














LAYING OUT THE WORK, 


24/ 


sewer are placed the same distance above the sewer-invert, 
and the cord stretched from one to the other is therefore 
parallel to the grade, which can be found at any point by 
measuring the given fixed distance down from the cord. The. 
cord is also vertically above the centre line of the sewer. If 
the trench changes in depth or for some reason it is desirable 
to change the distance from the cord to the sewer-invert, a 
step up or down must be made at some grade-plank by cutting 
two notches one or two feet apart in elevation. The cord 
should be strong linen fish-line or similar material whose light 
weight will prevent unnecessary sagging, and should be 
stretched tightly between the grade-planks. 

Another method of supporting the string is to drive at 
equal intervals stout stakes, at least 2 inches X 4 inches X 5 



feet in dimension, on each side of and about 3 feet back from 
the trench, and in pairs directly opposite each other. On each 
of these is found a point a certain whole number of feet above 
the sewer-invert and usually 2 or 3 feet above the ground, 
and a straight-edged board or plank is nailed, one end to each 
stake, with its upper edge exactly at these points. On this 
edge is marked the centre of the trench and a slight notch 
cut there to receive the cord. One end of the cord is fastened 
to a nail driven into the first board below the notch, and rests 

















248 SEWERAGE . 

in this notch and those of succeeding boards, and is fastened 

at its other end to another nail placed as 
is 

shown in Fig. 7 and caught behind the 
board, the cord being fastened in it and 
being readily tightened whenever it be¬ 
comes loose. This method of elevated 
^Holding 1 Grade- grade-boards is particularly applicable to 

large pipe sewers or small brick ones, since, 
the cord being higher above the ground, it interferes less with 
the lowering of materials into the trench. In some cases it is 
not wise to adopt it on account of the liability of the banks to 
be caved in by the driving of the posts. 

In laying pipe sewers from the cord a grade-rod is used 
with a mark or notch on its edge so placed that when it is 
level with the string the foot of the rod is level with the 
sewer-invert or with the outside top. The former is prefer¬ 
able, since the invert is the part of the pipe which it is most 
important to have at correct grade, and, as the pipes often 
vary slightly in diameter, this result may not be obtained if 
they are graded by their tops. If the inverts are to be set 
it will be necessary to have an offset-piece 
at the foot of the grade-rod which can 
rest inside the pipe upon the invert. For 
this purpose an ordinary cast-iron 6- or 
8-inch bracket, obtainable at any hard- 
ware-store, will answer; or wrought iron 
may be used if about \ inch thick and 
stiffened by being bent back upon the 
rod. The mark on the grade-rod should 
be checked each day. Fig> 8 - Grade-rod. 

For brick sewers each templet is set by a rod, and for both 
these and pipe sewers another rod is used by the foreman for 
getting the excavation to the proper depth. 



the first. Or a large spool is cut as 



















LA YING OUT THE WORK. 


249 ' 


The grade-plank or stakes above described can be set out 
even before excavation is begun, but except in shallow 
trenches it is better to wait until the trench is at least 6 feet 
deep, that they may interfere with the excavating as little as 
possible. It is often well, however, to drive the stakes, where 
these are used, before excavating to prevent cracking the 
bank, the board not being nailed to them until afterward. 
The grade-plank and stakes should be tested for grade and 
line at least once a day, and the inspector should keep close 
watch of them to see that they are not disturbed and also 
that the cord is kept taut. 

When excavating-machinery is used the grade-planks 
cannot ordinarily be placed above the surface, but they can 
be sunk into the ground entirely below the surface, or the 
bracing of the trench can be utilized by nailing the vertical 
strips to it. This latter method is also preferable for pipe 
sewers when the trench is very deep, since, if the cord is at 
the surface, the grade-rod is too long for convenience and 
accuracy, and the inspector is too far from the work of sewer 
construction to watch properly both it and the grade-rod. 

In trenches through running- or quicksand unless the 
utmost care is taken the banks will settle several inches or 
even feet, carrying the grade-plank with them of course. 
Under such circumstances a level should be kept constantly 
on the ground and the grades checked every few minutes 
during pipe-laying or at the time of setting templets. More¬ 
over, the bench-marks themselves, when on curbing, fire- 
hydrants, or elsewhere near the roadway, may settle and 
should be checked daily. > 

For properly fixing the grade of a manhole-head a stake 
may be driven near by indicating the street grade, and it 
would also be well to test the head by the level as it is being 
set. Similar stakes should be set for storm-water inlets. 


250 


SE WEEA GE. 


Inlet- and house-connections should be laid as truly to line 
and grade, and in the same way, as the sewer itself. 

Where grade-stakes in the bottom are used these are set 
to the exact grade of the invert or one foot above it. For 
pipe sewers the bottom of the trench is then given a uniform 
grade from one stake to another by using a straight-edge, 
stretching a cord, or too often by eye only, and the pipe is 
laid on this bottom and lined in by eye. Great accuracy can 
Jiardly be expected by this method. For brick sewers, how¬ 
ever, it compares favorably with the cord for accuracy (but 
mot for convenience), the stakes being driven in the centre 
line of the sewer and at such distances apart that each templet 
can be set close to a stake. 

Stakes driven upon the bank are not recommended for any 
purpose, it being almost impossible to obtain accurate results 
by their use. Their only advantage is that setting them 
gives less trouble to the engineer than either of the other 
methods. 

Alleged sewers have been laid with a carpenter’s level 2 feet 
long, to the under side of one end of which was fixed a piece 
of wood or iron or a screw protruding an amount equal to the 
desired rise in that distance. It would be an exceptional case 
in which a line of sewer so laid did not vary more than one 
inch in each ioo feet from the desired grade. 

While giving grades the measurement of the sewer-lines 
should be carefully made and noted and compared with the 
original measurements, and if any appreciable difference is 
found the sewer grades upon the plans must be readjusted to 
•correspond. Careful notes should be kept of all instrumental 
work connected with giving line and grade. It will be con¬ 
venient to have in each level-notebook a list of all bench¬ 
marks in the sewer-district in which it is to be used. 

Both inspector and engineer should watch for the first 
indication of the existence in the trench of an obstruction to 


LAYING OUT THE WORK . 


251 


the sewer, that preparation may be made for a change in line 
or grade if necessary to pass the obstruction. Such change, 
if in line, may necessitate inserting one or two additional 
manholes or a lamp-hole; if in grade it may be made by a 
decrease in grade in one stretch and an increase in the next, 
or by siphoning under or over the obstruction (see Art. 49). 
In some cases the change can be made in the obstruction and 
not in the sewer. 

It is the inspector’s duty to see that house- and inlet-con¬ 
nection branches are inserted at the proper points, and their 
exact locations noted, which locations the engineer must make 
note of and reference to some fixed point, usually the centre 
of the nearest manhole, to make possible the ready finding of 
the branches in the future. This is very important and should 
be faithfully attended to. 


CHAPTER XII. 


OVERSIGHT AND MEASUREMENT OF WORK. 

Art. 65. Inspection of Work. 

The specifications are practically the instructions to the 
contractor as to the way in which the sewerage system is to 
be built, the lines, grades, and dimensions being given by the 
engineer, chief or assistant. If the contractor were left 
unwatched to carry out these instructions it would be impossi¬ 
ble to know whether he had done so or not, since only the 
inside of the sewer can be examined, and this only with diffi¬ 
culty. And if it were found, after the completion of the 
work, that it had been improperly built or of poor material, 
even though the contractor could be compelled to replace it 
with satisfactory work, the delay and inconvenience of this 
might better be avoided by proper oversight during construc¬ 
tion. It is advisable, therefore, that a competent inspector 
be constantly on hand when any construction is progressing. 
This is not necessary during excavation, but even this should 
be looked after at least once a day, that any unforeseen 
underground condition which may modify the plans may be 
noted, and in general to ascertain that the contractor is 
obtaining the proper width of trench, is not interfering un¬ 
necessarily with private drains, water- or gas-pipes, and is in 
general following the directions for trenching, blasting, etc. 

For this oversight it will usually be necessary to have an 
inspector for each set of pipe-layers and of masons. But if 


252 


OVERSIGHT AND MEASUREMENT OF WORK. 253 

only one or two trenches are being worked at a time the 
instrument-man may also be inspector. The omissions and 
poor work which may be accepted from the contractor if such 
inspection is not constantly made may be seen from a state¬ 
ment of the inspector’s duty. 

The inspector should be on hand before work is begun at 
morning and noon to see that no mortar left from the previous 
day is worked over, that new mortar is properly proportioned 
and mixed, and to examine grade-lines or -stakes. In the 
case of pipe sewers he should examine the inside of the sewer 
near the end and see that any stones, dirt, or other matter 
which may be there be removed before the laying begins. 
He should also examine the one or two cemented joints 
nearest the end, and if they are not sound the pipe should be 
removed and relayed. In the case of brick sewers he should 
examine the toothing at the end of the brick-work and have 
removed any loose brick and all mortar and dirt that may be 
lodged there. 

He should continually keep an eye upon material and 
workmanship, examining each pipe before it is lowered into 
the trench, each load of brick and of sand as they are brought 
upon the ground, each barrel or bag of cement to see that it 
bears the engineer’s mark or is of the required make and that 
it is not caked by moisture. He should see that the proper 
proportions of cement and sand are used for the mortar, and 
that no mortar partially set is retempered and used. 

On brick sewers he should see that each templet used is 
one approved by the engineer and that it is set to the proper 
grade and line, that the brick are laid to line and in accordance 
with the specifications, that slants or other branches are set 
where needed, and he should keep an accurate account of 
these, their size and length, and mark the position of each by 
a stake driven in the bank directly over it for the information 
of the engineer. He should see that the arch-centre is solid 


254 


SEWERAGE. 


and does not spring under the brick-work, and that it is not 
drawn too soon. 

On pipe sewers he should see that each pipe is laid to 
grade and line by the use of the grade-rod and a plumb-bob 
in connection with the grade-cord, that each pipe is pushed 
‘‘ home,” each joint properly cemented and the swab or piston 
in the sewer pulled forward, and that the back-filling is 
properly placed and tamped around the pipe. He should see 
that house-branches are placed where directed, that covers 
are cemented in each one (about this he is sometimes careless, 
to the great detriment of the sewer), and should drive a stake 
in the bank directly over each. 

He should keep a record of all extra work, or work, such 
as foundations or sheathing left in the trench, which cannot 
be measured after the completion of the sewer. 

If the ground is wet he should see that no water flows 
over the brick-work or through the pipe, except as permitted 
by the engineer. In general he should be thoroughly familiar 
with the specifications and have a copy constantly on the 
work, and see to their enforcement, reporting to the engineer 
any difficulty in obtaining this. 

He should not be permitted to be in any way indebted to, 
or under the influence and power of, the contractor, and 
should receive orders from the engineer only. 

He should be a man with some experience in the character 
of work he is inspecting, sober, and having the respect of the 
contractor and workmen. 

Art. 66 . Duties of the Engineer. 

The engineer should keep constantly in touch with the 
work, visiting each point at least once a day, and giving 
necessary instructions to the contractor and inspector, as well 
as giving and testing line and grade. If he has many 


OVERSIGHT AND MEASUREMENT OF WORK . 255 

inspectors on work under his charge they should be required 
to report at the engineer’s office after each day’s work the 
amount done and return a detailed statement of any extra 
work, asking instructions on any points concerning which they 
are in doubt. The daily reports may be made in writing upon 
blanks furnished to the inspectors for this purpose. 

The engineer must see that each inspector is performing 
his duty, and if necessary enforce instructions given by him 
to the contractor. He must inspect all material to be used, 
where this is possible, or give the inspector full instructions 
on this point where it is not. It is well to mark each accepted 
barrel or bag of cement; to inspect the pipe after it is deliv¬ 
ered upon the street, but well in advance of the laying, seeing 
that all defective pipe is removed; also to inspect and weigh 
all iron-work before it is used. 

The engineer must decide where and how much sheathing 
shall be left in the trench, making a note at the time of its 
exact location and length, must decide as to the classification 
of the material being excavated, and must measure promptly 
all material classed as rock. He should each day take measure¬ 
ments necessary to locate the house-branches as indicated by 
the inspectors’ stakes. It is well to measure each stretch of 
sewer, each manhole and other appurtenance as soon as com¬ 
pleted. 

The engineer should see that the contractor respects the 
rights of property-owners and keeps the streets and sidewalks 
open where possible, that the laborers are efficient and, where 
necessary, skilled in the work to which they are assigned, and 
that they create no disturbance along the streets in any way 
for which the contractor is responsible. He should compel 
the contractor to work with sufficient force and in such a 
manner as will lead to the completion of the work in the 
specified time, to place such shoring and sheathing as may be 
necessary to prevent any accidents to property or lives or to 


256 


SEWERAGE. 


the sewer, to provide pumps in sufficient number and of 
ample size to handle all ground-water, and to use excavating- 
machinery where necessary. In general he should see that 
the work is carried on by proper methods, with proper 
materials, with a force and a plant satisfactory in both char¬ 
acter and extent, and that the inspector enforces his directions 
as to details. 


Art. 67 . Measurements. 

The specifications should state in what way the measure¬ 
ments shall be taken for each description of work or material. 
The measurements so made for the final estimate (which is 
the name customarily given to the measurements and calcula¬ 
tions on which is based the -final payment for a piece of 
work) should be accurately and carefully taken and checked 
at least once, as should be the calculations based thereon. 
The engineer should be able to swear upon the witness-stand, 
as he may be called upon to do, that the final estimate is a 
truthful and correct statement of the work actually done. 
Quantities given in this estimate should be stated in the units 
used in bidding for the work. 

Measurement of the sewer laid is usually made from centre 
to centre of manholes, flush-tanks, etc., not horizontally, but 
parallel to the sewer (the surface of the street being practically 
this in most cases), no deduction being made for branch 
specials or the lengths of manholes. Payment is sometimes 
made uniformly for all depths of sewer, sometimes varying 
with varying depths. The latter seems the fairer way, par¬ 
ticularly where some lines contracted for may be omitted or 
new ones added. Usually no changes in price are made for 
less differences in depth than two feet, the measurement being 
made from the surface to the under side of sewer or of foun¬ 
dation-platform. These depths are ascertained from the 


OVERSIGHT AND MEASUREMENT OF WORK. 2$? 

profile, on which are plotted the surface grade and the sewer. 
Since for the original profile elevations were in general taken 
at ioo-foot intervals only, and as a check on these, the eleva¬ 
tion of the surface should be taken and noted at each grade- 
plank when grade is being given for sewer construction. 

The depth of each manhole, lamp-hole, and other appur¬ 
tenance should be obtainable from the profile, but as a check 
each should be measured with a levelling-rod or tape. Each 
manhole, lamp-hole, flush-tank, and inlet should be designated 
by a number, by which it is referred to. It is almost impos¬ 
sible otherwise to correctly count and keep track of these, 
especially the manholes, so many of which are each common 
to two lines of sewer. 

Inlet-connections may be measured from their upper end 
to the shoulder of the branch or slant. Whatever the limits 
to be taken they should be carefully set forth in the specifica¬ 
tions. 

Rock should be measured before excavation in most 
instances, although its original surface can often be judged 
afterward by that showing along the sides of the trench. If 
the rock-surface is fairly even and uniform readings may be 
taken at intervals of io feet; but if it be uneven and jagged 
these should be, not at regular intervals, but wherever neces¬ 
sary to give accurate results. All measurements, whether of 
earth, rock, sewer, or manhole, should be taken to tenths of 
a foot. It is customary to allow the contractor a certain 
cross-section of trench, and pay him nothing for excess exca¬ 
vation nor deduct for a less area of section. But the trench 
at the bottom should be kept the full width called for. 

A final-estimate book should be kept, in which is entered 
an exact statement of each piece of work as it is completed, 
but not before then. The measurements should be classified 
under the items for which bids were received, and the location 
of each given; thus: 


258 


SEWERAGE. 


8-INCH SEWER, 8 TO IO FEET DEEP. 

Location. Length. 

From manhole No. 7 to manhole No. 8 3 2 7*3 feet 

Between manhole No. 8 and manhole No. 9 39 -° ** 

8-INCH X 4-INCH Y BRANCHES. 

Location. Number. 

Between manhole No. 7 and manhole No. 8 13 

“ “ “ 8 “ “ “ 9 11 

MANHOLES. 

No. of Manhole. Location. Depth. 

7 Main Street, between Clinton and Madison 9.2 

8 Corner Clinton and Main streets 9.2 

A pocket field-book should be constantly at hand, in which 
are entered all measurements taken, the points of the begin¬ 
ning and ending of “ sheathing left in trench,” of sub-drains, 
of foundations, the location of all Y’s, the details and quan¬ 
tities of “ extras,” the location of underground structures for 
future reference, and the date of beginning and ending of 
construction on each stretch of sewer. These notes should 
be copied every evening into an ofifice-book, since a loss of 
these data would be serious and irreparable. The general 
appearance of such notes is shown on page 259. 

It is well also to have a pocket copy of the profile of each 
street, showing the sewer as designed, with size, grade, eleva¬ 
tion, location of manholes, flush-tanks, and other appurte¬ 
nances. This method of taking these data to the field for use 
seems to be more complete and convenient than copying them 
down into a notebook. 

According to most contracts the contractor must be paid 
monthly, and for this purpose monthly estimates must be 
made by the engineer. He should estimate each month the 
total amount of each item completed to date, from which is 
deducted the total estimated the month previous, the differ¬ 
ence being the amount performed during the month. This 
method prevents the carrying ahead or accumulation of any 
errors which may be made in any one monthly estimate, which 
errors are liable to occur owing to the fact that such estimate 


M.H.^8 * Sta. 16+73.3 M.H.\ 9.2' deep. 


OVERSIGHT AND MEASUREMENT OF IVOR A 


259 




Begun June 3 d 
Completed “ 6 th 


Begun June 4th 
Completed “ 7 th 




*0 
f 

-A 


o 

to 

X' 

GO 

X 

to 

05 

ds" 

0^1 

0^1 

Co 

c- 4 - 

o 

TO 

a 

TO 

(-*■ 

to 


<-+■ <s>i 

a =S 

:£?? 

CO 

.4"^ 
’3 S' 

■ § 
to -$ 

S § 


< 0 . 

a 

to 

to 


cS 

to 


W .o' 

o«4 

<s> 

<Q 

r-K 


&Q Gq 

S' >* 

W Cb 

• a 


CO 


If*. 


> 

o 


Go 

<fK 

a 


a* 05 

co ^ 

** 5* 

Sr 4 05 

s* ^ 

ft 4 


I If* 

+* 3 

07 CQ 
to ^ 

• <f-g 

Ok 

rS»* 

3 

> 

o 


Go 


05 

4* 

<? 

CO 

OK 

o 


SP 

o 4 

I 

a, 

** 

a 

<s>. 

s 

TO 

3 

a, 

00 

a 

<fK 


CD 

4- 

o 


E3 




CO 

to 

a,' 

.TO 


to 

o 

s 

<-x 

a 

TO 

a 

<CK 

Gq 

<f«t. 

a 

to 

l-l 

-+ 

to 

Or 


GO 

TO 

a 

<«S 

a 

CO 


(Left hand page of note book.) (Right hand page of note book.) 

m.h.% 0 sta. 22+85.1 M.h\ 8.7' deep. 

„ _ _ . .1 t 

Madison 10 Water Main sta. 22+79 St. Water main 4 above sewer invert. 






















I 


260 SE WEE A GE. 

must often be made hastily and simultaneously with the 
oversight of construction-work. Uncompleted work must be 
estimated according to the judgment of the engineer as 
• equivalent to so much completed work of the same class. 

For the final estimate all measurements as given in the 
final-estimate book should be checked with the field-book and 
in every other way possible, and every precaution taken to 
secure absolute absence of error in measurements or calcula¬ 
tions. As a check upon the estimate it would be well to 
obtain from the contractor the bill of pipe, brick, and iron 
used by him upon the work, allowance of course being made 
for material condemned or unused. 

Art. 68. Final Inspection. 

The final inspection of the work before its acceptance from 
the contractor should be thorough, and made by the engineer 
in person or by an experienced, trustworthy assistant. He 
should enter every flush-tank, manhole, inlet, or other appur¬ 
tenance sufficiently large for this, taking its dimensions, notic¬ 
ing whether the head or grating is at the proper level and 
substantially set, the brick-work smooth, the form regular, 
the steps properly set at the prescribed intervals, that no 
ground-water leaks through the brick-work, that pipes passing 
through the walls are properly built in with surrounding 
“bull’s-eyes;” that the bottoms of manholes are formed ac¬ 
cording to instructions, the invert-channel being straight or 
with a uniform curve, of the proper width, and its grade uni¬ 
form through the manhole and of the proper elevation, and that 
the benches have the specified slope; also, if there are sub¬ 
drains, the hand-holes should be inspected, and these as well 
as the manholes should be free from dirt. Lamp-holes should 
be inspected by lowering a lamp into each and noting whether 
it is straight and vertical, and by seeing that the heads are 




OVERSIGHT AND MEASUREMENT OF IVOR AT. 261 


set according to specifications and at the proper grade. 
Flush-tanks should be filled with water and tested for tight¬ 
ness for at least 24 hours, during which time the water-level 
in them should not lower more than one or two inches. If 
automatic flushing apparatus is set it should be tested with a 
stream sufficiently small to fill it in not less than 24 hours. 
To expedite the test it can be rapidly filled and discharged 
once to test its proper working, then rapidly filled three 
quarters way to the discharging-point and the inflowing 
stream cut down to the rate above mentioned, to see that the 
siphon does not trickle,” but holds the water until the 
height is reached calculated to cause a complete siphoning of 
the water in the tank. 

Every foot of sewer and inlet-connection should be in¬ 
spected. Sewers 24 inches or over in diameter should be 
entered and each joint inspected, if they are pipe sewers, to 
see that no jute or cement protrudes into the sewer and that 
there is no leakage. In case of the former the protruding 
cement or jute should be removed; and if there is leakage 
this should be stopped, for which purpose there may be calked 
into the joint from the inside dry cement immediately fol¬ 
lowed by jute, cloth, or similar material to hold it in place 
until set; or wooden wedges, or tea-lead may be used. If 
these or similar methods fail it may be necessary to uncover 
the pipe and apply additional cement on the outside, backed 
and supported by concrete if necessary. Any cracked or 
broken pipe should be dug up and replaced. The branches 
should be examined also to see that a water-tight cover is in 
each one which is not already connected with a house-drain. 

If the sewer is of brick the brick-work should be smooth, 
with struck or pointed joints and without any cracks. To 
determine whether the form and dimensions are as specified 
a skeleton templet may be used. If the sewer is circular this 
may consist of two light rods, each of a length equal to the 


262 


SE WEE A GE* 



nominal interior diameter, and connected by a bolt passing 
loosely through holes at the exact centre of each. One of 
these rods is to be held stationary across the sewer and the 
other revolved upon the bolt, when each end of the latter 
should just touch the sewer through the entire revolution. 
For an egg-shaped sewer a half templet may be used. Slants 
or other branches should be examined as stated for pipe 

branches. Special attention should be paid 
to junctions of brick sewers to see that the 
curves are easy and uniform in plan and that 
the arches are strong and well built. All 
spalls, bats, plank, and other refuse and dirt 
should be removed from the sewers. If 
brick sewers leak the joints may be calked, 
as suggested for pipe-sewer joints. For 

such inspections a lantern with a reflector is 

Fig. o.—Inspector’s , . , , 

Templet for Egg- desirable. 

shaped Sewer. Inspection of small pipe sewers can be 

made from manholes only. As a test for straightness a light 
held at the opening of the pipe in a manhole or lowered into 
a lamp-hole should be distinctly visible from the next man¬ 
hole. Further inspection can be made by the use of mirrors 
from which light is reflected into the sewer. The simplest 
plan is to reflect the sunlight from a mirror held by an assist¬ 
ant on the surface to another mirror held by the inspector in 
the manhole, who so manipulates his mirroi as to throw a 
spot of light onto each length of the sewer in succession, 
meantime inspecting the same by looking past the mirror into 
the sewer. This generally requires that he kneel in the man¬ 
hole upon the side benches, his back to the sewer to be 
inspected, his head bent down until he can see into the sewer, 
and the hand which holds the mirror thrust back between his 
legs. It is advisable that he have pads for his knees if he 
have many sewers to inspect in this way. Apparatus has 






OVERSIGHT AND MEASUREMENT OF WORK. 263 

been devised for removing some of the inconveniences of this 
method by so placing an additional mirror that the interior 
of the sewer is reflected therein, and the inspector is relieved 
of the necessity of assuming an uncomfortable position. Such 
an apparatus is described in Engineering News, vol. XXXII, 
page 249. 

The imperfections most commonly found in pipe sewers 
are: loops or ends of oakum or ridges of cement protruding 
into the sewer at the joints; dirt, stones, etc., in the sewer; 
uneven grade, which can be detected by allowing a small 
amount of water to flow through the sewer, which stream will 
be wider at the depressed and narrower at the elevated points; 
ground-water leaking in through the joints; broken pipe; 
breaks, at joints, in the continuity of the invert-surface. 

The last defect can be remedied by relaying the pipe, or 
by drawing through the sewer an “ invert-former ” filled with 
thin neat Portland-cement mortar (slow-setting). This is 
essentially a box, its bottom of the shape and size of the 
sewer-invert, through a large opening in which the cement 
passes to the sewer, to be pressed into shape by the rear end 
of the box as it passes over it. The box is heavily weighted 
to force ahead the surplus cement. It can be made of thin 



sheet iron bent to the proper shape and stiffened by inside 
partitions cut from plank. Broken pipe and leaking joints 
can only be repaired by digging down to the sewer (see, how¬ 
ever, Art. 85). Dirt, stones, and protruding cement may be 

































264 


SEWERAGE . 


removed by drawing a scraper through the sewer by means of 
a rope, or by pushing it through by a rod formed by jointing 
together several shorter rods of a size which can be introduced 
through a manhole—about 5 feet. A stream of water from a 
fire-hose nozzle under a good head can be used to remove 
from a stretch of sewer not more than 300 feet long almost 
anything less in size and weight than a brick. The hose 
while water is passing through it is so stiff that it can be 
pushed for a long distance into the sewer. Jute ends or 
loops are sometimes difficult to remove, but can usually be 
cut off by a sharp knife-blade fastened to a long rod, or 
burned off by putting under them (they generally hang from 
the top of the sewer) a small lamp or candle similarly fas¬ 
tened. Or, if there is water flowing through the pipe, the 
candle may be fastened to a piece of wood or cork to which 
a string is attached and floated down to the desired point. 
The exact distance from the manhole of any defect can be 
ascertained by counting the number of pipe intervening. 

Sub-drains should be inspected by turning into each 
stretch for a short time all the water it can carry (if they are 
not already running full) and watching for indications of 
stoppages. The apparatus for inspecting sewers above 
referred to may in some instances be used for sub-drains, 
being lowered into the sub-drain hand-hole. If any drain is 
entirely stopped this may be remedied by the use of rods, 
fire-hose, “ pills ” (see Art. 85), etc.; or it may be necessary 
to locate the obstruction and dig down to it. 

As far as possible assurance should be had by examination 
that all the conditions of the contract have been carried out, 
those having reference both to the construction and to the 
more strictly business relations between city and contractor. 


CHAPTER XIII. 


PRACTICAL SEWER CONSTRUCTION. 

SEWER construction is sometimes undertaken by the 
city under the immediate supervision of the engineer, who 
should in such a case be well informed in practical construc¬ 
tion methods. He would also be better fitted by such infor¬ 
mation to design a system and to oversee it if constructed by 
a contractor. This chapter is intended to give some informa¬ 
tion on this subject based upon practical experience. It is 
not pretended that the entire field is covered, but it is 
thought that the student and those with little experience in 
sewerage-work, and perhaps others, will find the information 
given of considerable value. 

Art. 69. Organizing the Force. 

The number of men which can be worked in one gang 
economically depends upon the character of soil, depth of 
excavation, amount of ground-water, manner of construction 
of the sewer; also upon the personality of the general foreman 
and contractor. If the soil is “ rotten,” with little cohesion, 
very wet, or the trenches very shallow, the gangs should be 
small; but if the ground is dry and stands up well or the 
trenches are deep larger gangs can be used. With the 
increase in the number of gangs comes increased difficulty in 

seeping them all supplied with materials and tools and work- 

265 


266 


SE WEE A GE. 


ing to an advantage. Good foremen are a necessity if there 
are to be more than two or three gangs, since it may at times 
be necessary to leave them to carry on their work for days at 
a stretch with no more than a hasty daily visit from the con¬ 
tractor or genera] foreman. A foreman who can keep the men 
faithfully at work without favoritism or making himself gen¬ 
erally hated by them, who has sufficient intelligent foresight 
to arrange their work a day or two ahead, to never be out of 
sheathing, cement, sand, brick, or other material, who has a 
practical knowledge and knack for overcoming difficulties, and 
who can be depended upon to be sober from the time the 
work starts until it ends—such a man is valuable upon sewer¬ 
age-work. But if such men cannot be had it will be better 
to work only two or three gangs, all of which can be kept 
under the contractor’s or engineer’s eye. 

The city engineer or the contractor, as the case may be, 
if he does not himself devote his entire time to it, should have 
a general foreman over the entire work. There should be a 
foreman over each gang, and if the number in a gang exceeds 
30 an additional foreman; also in each a water-boy to carry 
drinking-water and run errands. If the trenches need sheath¬ 
ing there should be on each, under the direction of the fore¬ 
man, from one to three men handy and experienced in such 
work. 

It will be necessary to sharpen the picks frequently, even 
twice a day in flinty hard-pan or gravel, and for this purpose, 
as well as to repair shovels, wheelbarrows, axes, chains, etc., 
a blacksmith should be established handy to the work. When 
not engaged on such repairs he can be making manhole-steps, 
calking-irons, etc. 

There should be a timekeeper, if the force is large, to 
take the time daily and make it up for each pay-day, who 
may also serve as clerk, keeping account of all material 
received and where delivered, ordering new when so in- 


PRACTICAL SEWER CONSTRUCTION. 267 

«' v * * 

structed, and keeping a daily account of the work done by 
each gang. 

Two pipe-layers may be connected with each gang if the 

\ 

trench can be rapidly excavated; otherwise two or more gangs 
may have a pair of pipe-layers in common, who lay pipe first 
in one trench and then in another, as sufficient length of each 
is excavated. For manholes, flush-tanks, and other masonry 
appurtenances a mason and two helpers may work together, 
passing from point to point as needed. For brick sewers two, 
four, or even six or eight masons may work together, the 
number in a gang usually being even. The number of masons’ 
helpers depends somewhat upon the depth of the sewer, one 
or more extra ones being required to lower brick and mortar 
if the depth is considerable. For a depth of 8 feet or less 
approximately the following will be needed: two masons, four 
helpers; four masons, seven helpers; eight masons, fourteen 
helpers. 

Besides the teams employed in hauling material to the 
work there should be one for carrying from place to place 
mortar-boxes, tool-boxes, and other heavy articles. 

It is difficult to say anything definite concerning the 
number of men which should form an excavating-gang. There 
should be sufficient to keep the pipe-layers or masons con¬ 
stantly at work. Each gang or set of gangs to which a pair 
of pipe-layers or force of masons is assigned should be just 
large enough to open and back-fill trench at the average rate 
at which the sewer is laid. If the sewer frequently varies in 
depth or ease of digging it is often well to assign a force of 
masons or pipe-layers to two gangs, always endeavoring to so 
arrange that one of these is in soil rapidly trenched whenever 
the other is in deep or difficult work. For 8-foot excavation 
in good soil requiring little bracing 25 to 30 men at the shovel 
is usually an economical number; at 15 feet, if no excavating- 

C 

machinery is used, 60 to 80 will be required for equally rapid 


268 


SE WEE A GE. 


work. On account of the considerable sheathing necessary at 
such depths and for other reasons it may be better, however, 
to still maintain the gang at 25 or 30 men, and assign the 
sewer-masons or -layers to two gangs. It is usually undesir¬ 
able to change the size or personnel of gangs after they have 
once been gotten into good working shape. 

If a trench runs into very wet soil or quick or running 
sand gangs as large as the above cannot be used to advantage, 
since not only must sheathing be set and driven right up to 
the excavation as it proceeds, but the pipe or sub-drain must 
be laid or foundation put in foot by foot as the bottom of the 
trench is reached; also an upheaval of the quicksand bottom, 
caving, and other accidents may cause occasional stoppages of 
the work for a few minutes, when almost the entire gang 
must lie idle or go to back-filling. In such difficult work on 
pipe sewers a gang may consist of a foreman, a sheather, two 
pipe-layers, and five or six laborers. If the ground is very 
wet it is advisable to open only a little trench at a time, since 
the more that is open below water-level the greater the 
amount of water which will flow through the trench and inter¬ 
fere with the work. Under such circumstances the gangs 
should be small. 

If the back-filling is not to be rammed it is the custom of 
many contractors to use the entire gang for the last 20 to 30 
minutes each day in back-filling. This arrangement has the 
advantage of not requiring an extra gang and foreman for 
back-filling. But if there are three or more gangs excavating 
it would perhaps be better to keep one gang continually back¬ 
filling. This is certainly advisable in all cases where the 
trench is to be thoroughly tamped. 

The contractor, general foreman, or timekeeper should 
visit each gang just after the beginning and just before the 
ending of each day’s work, at the least, to learn of any 
material needed or difficulty encountered, and also to get the 


PRACTICAL SEWER CONSTRUCTION. 269 

\ 

“ time ” of the men, which may have been taken by the fore¬ 
man, or may better be taken directly by one of the three 
above mentioned. 

If Italians or other non-resident workmen be employed 
(and if the work is in a small city and requires many men 
outside labor must be obtained) they are usually housed 
together in barns or empty houses or shanties constructed 
for the purpose on the outskirts of the city. If these can be 
located near a stream the men will usually take advantage of 
the opportunity to wash themselves and their clothes and keep 
in better health than if otherwise situated. The necessity for 
walking a long distance to and from work will result in 
decreased energy in their labor, and should be avoided. It 
will sometimes pay to have the teams carry them to and from 
the work. It will also be to the contractor’s advantage to see 
that their food is wholesome. A considerable experience with 
Italian laborers has convinced the author that as a class they 
are more appreciative than are native laborers of both kind¬ 
ness and harsh treatment, and are shrewd readers of motives 
of conduct. If justly though firmly treated they are polite, 
obedient, and good workers, slow to wrath, but dangerous if 
ill treated. “ Sore-heads ” among them should be gotten rid 
of at once. 

Fay-days should come at as long intervals as possible, 
because of the diminished force which can be made to work 
for the following day or two, if for no other reason. For some 
reason masons seem to be peculiarly subject to the failing of 
“ pay-day drunks,” and if possible an arrangement should be 
made with them to pay their expenses wherever they wish to 
board and a small weekly amount of pocket-money, the 
balance being paid them when their work is completed. 
Monthly payments are generally made to the laborers, imme¬ 
diately after the payment of the monthly estimates. 


270 


SE WE JR A GE. 


Art. 70. Trenching by Hand. 

The line of the trench being given by centre stakes, the 
sides of the excavation are indicated by measuring the proper 
distance on each side of the stakes and stretching sash-cord 
or clothes-line there and marking the ground along this line 
by means of a pick. The laborers are then placed at regular 
intervals along the trench, varying from 6 to 20 feet, in single 
line in most cases, but if the trench is 8 feet or more wide 
they may be in double line. It may be well to define in some 
way, as by a mark in the ground or stake at one side of the 
trench, equal lengths of trench, one man being required to 
work within the limits of each length. Where possible it is 
desirable that this length be that which can be completed in 
a half or a whole day. 

If the street is macadamized or gravelled or has a hard dirt 
surface a contractor’s “ rooter plow ” may be used to break 
the surface; but this is not advisable in narrow trenches, nor 
should the surface be broken beyond the sides of the trench, 
since if sound it helps to prevent caving of the sides. 

If there is any paving material on the street it should be 
thrown upon one side of the trench, and the remaining 
excavated material upon the other side, the material on each 
side being kept back a foot or two from the edge of the trench 
to allow a pathway for foremen and inspector and for lowering 
material, but still more to prevent excavated material from 
falling back into the trench. Thus one side of the street is 
left open to travel, the pile of paving material acting as a guard 
to the trench on that side. If so much soil is to be thrown 
out or the street is so narrow that it cannot all be placed upon 
one side of the trench it may be placed upon both sides, the 
paving material being kept separate, say along the outside 
edge of one bank; but it would be better to use excavating- 
machinery and thus avoid blocking the street entirely. The 


PRACTICAL SEWER CONSTRUCTION. 


271 


amount which can be placed upon one side of the street with¬ 
out covering the sidewalk may be increased by setting there 
a platform and guard, as shown in Fig. 11. 

The first earth cast out should be thrown to what will be 
the outside edge of the bank, since it cannot be thrown there 
when the trench is deeper without double handling. The 
gutters should be kept open and free from any excavated 
material. Down to a depth of 9 to 12 feet the earth can be 
cast to the surface, although after 5 or 6 feet is reached it will 



Fig. ii.—Excavation-platform. 

be necessary to keep additional men on the surface to throw 
back onto the pile the material so cast out. When the depth 
exceeds 9 to 12 feet it will be necessary to handle the material 
twice before it reaches the surface, by placing a platform or 
staging about 6 or 7 feet below the surface, onto which the 
earth is thrown by two to four men, and from which it is 
thrown to the surface by one man. If the depth exceeds 16 
or 18 feet still another platform will be necessary about 7 or 
8 feet below the first. These platforms are usually made by 
resting plank upon the braces or rangers of the sheathing. 
(Except in rock cuts there are almost no conditions under 
which a trench 10 feet or more in depth should be left 
unbraced.) The p'latform may consist of short pieces of plank 
placed crosswise of the trench, their ends resting on the 
rangers, or of long plank lengthwise of the trench resting upon 
the braces. The latter cannot well be used if the trench is 












272 


SE WE A A GE. 


less than 5 feet wide, but is the better form for wide trenches. 
If there is more than one tier of longitudinal platforms the 
successive tiers should be placed alternately upon -opposite 
sides of the trench; or if cross-platforms are used the right 
side of one should be vertically above the left side of the next 
lower, alternate platforms being vertically above each other. 
The number of men excavating which cast onto one platform 














/«V' 

1 



/////Awwv 

4 ^ 

/ 



1 






1 







V 1 

_ > 



A 

As/ 

A- 





A'' 

"A 

AA/ 




Fig. 12.—Cross-staging in Trench. 


may be only two, but should increase with the difficulty of 
excavating, so as to keep the staging-man busy. 

Where it is allowed (as it is in many cities), and the trench 
is over 10 feet deep, it is often economical, except in hard 
rock, dry sand, or quicksand, to make the excavation in alter¬ 
nate tunnels and open trenching, the sections of each being 8 
to 20 feet long. The tunnel is usually made about 5 feet 
high. , The amount of material to be removed and of bracing 
to be put in is thus reduced. But tunnelling should never be 
allowed under streets, except in rock, unless the tunnel is 
afterwards opened and back-filled as open trench, being used 
only to save bracing; since it is practically impossible to so 
compact the back-filling in a tunnel as to prevent future 
settlement, which may not occur, however, until months or 
years later, when the contractor has been relieved of all 



















































PRACTICAL SEWER CONSTRUCTION. 


273 


responsibility. Where the amount of traffic on a street or 
other conditions require it, however, a tunnel may be run 
under the street and a masonry lining, which may be the 
sewer itself, built against the outside of the excavation, so 
that there is no back-filling except in the form of masonry; 
which construction requires special tunnelling-machinery and 
methods. In Paris by the use of a shield a tunnel 19 feet 
outside diameter was run with a covering in some places of 
only 2 feet between it and the street-paving above, without 
causing any cracks in the latter. The successful tunnelling 
for the Boston underground railway is familiar to all. A 
notable instance of sewer-tunnelling is found in the sewers 
tunnelled through sand-rock at St. Paul, Minn., the tunnel, 
when lined on the bottom, constituting the sewer. Restric¬ 
tions against tunnelling should not of course apply to lines 
whose depth is 75 feet or more, such as those passing through 
ridges. 

There is a tendency, if a right-handed laborer always faces 
one way while picking, for the trench to work to his left as it 
descends. He should be taught to avoid this by keeping his 
left side to the side of the trench at which he is picking, so 
that both sides shall make the same angle, if any, with the 
vertical. 

It pays to keep the picks sharpened and good shovels in 
the men’s hands. For this purpose there should be 25 to 100 
per cent more picks than laborers, to allow opportunity for 
sharpening them. For digging the round-pointed shovel is 
best, but staging-men and mortar-mixers should use square- 
pointed shovels. There should be a few extra shovels con¬ 
stantly on hand, including a few long-handled ones, but these 
latter should not be used for trenching except in deep 
trenches where the shovelling is very easy. 

In soil where caving is frequent and sheathing is not used 
the trench should be refilled as soon as possible, since the 


274 


SEWERAGE. 


longer it stands the greater the probability of caving. Soils, 
such as clay or other heavy ground, having some cohesion 
will usually give warning of caving by cracking a few feet back 
from the edge of the trench, and should be braced as soon as 
such sign appears. Gravelly soils or dry sand usually give no 
such warning, and are particularly dangerous on this account 
and because they may bury and suffocate the men; while 
clay, coming in lumps, although it may bury and even crush 
them, will permit them to breathe until they can be rescued. 
Trenches in gravelly and sandy soil should always be sheathed. 

If a boulder is met with it may be raised from the trench 
by a derrick or, if too large for this, may be blasted. Before 
blasting the earth should be removed from all sides of the 
boulder and the trench in the vicinity should be braced. It 
may sometimes be cheaper to dig a hole in the side of the 
bank and roll the boulder into this out of the way. In some 
cases, when the sewer would pass entirely under the boulder, 
this may be left undisturbed and tunnelled under. If it 
merely protrudes into the trench a portion may be removed 
by “ feathers and wedge or a heavy sledge. 

If a water- or gas-pipe or other conduit run diagonally 
across a trench, or run in it, or cross one more than 8 or io 
feet wide, it should be supported in position before the earth 
is removed from under it. This can be done by placing 
across the trench at intervals of 12 feet sufficiently strong 
timbers or old rails, and suspending the conduit from these 
by chains drawn tight by driving wedges between them and 
the beams. Rope should not be used for this purpose, as 
rain causes it to contract or break in the attempt to do so. 
If such a pipe lies in the bank, close to or slightly protruding 
into the trench, the bank should be thoroughly braced just 
under the pipe and the pipe itself be held in place by braces. 
These braces should not be removed when the trench is back¬ 
filled, and if the pipe is suspended the trench should be filled 


PRACTICAL SEWER CONSTRUCTION. 275 

and thoroughly tamped under and around the pipe before the 
chains are removed. The breaking of a water-main in or near 
a sewer-trench is one of the most disastrous accidents which 
can happen to it. Small house-connection pipes crossing the 
trench are apt to be broken by workmen climbing over them 
and should be protected, as by a piece of plank or of a 
2X4 placed across the trench just above such pipe, the 
ends extending 6 inches or more into the banks for support. 
In all cases where there is danger from water-pipe such and 
so many gates should be temporarily dosed that the closing 
of only one more will entirely shut off the pressure from the 
threatening line of pipe, and a wrench be kept at hand for 
closing this. 

If a drain crosses the trench the pipe should be removed 
and saved, and a trough substituted during construction, its 
ends supported in the banks. The back-filling should be 
carefully tamped under this and the pipe relaid in the trough. 

At the first sign of quicksand the best of close sheathing 
should be at once put in, an experienced foreman put over 
this work and the best men placed upon it (see Art. 72). 

The soil where a trench has previously been dug, although 
it were years before, is more liable to cave than that which 
has never been disturbed, and the sewer-trench should be 
kept several feet from such old trench if possible. 

Art. 71. Excavating-machinery. 

As a general statement it may be said that it does not pay 
to use any kind of machinery in excavating where the trench 
is less than 8 or 9 feet deep or wide, although it may be 
desirable or necessary to do so where for some reason the 
excavated material cannot be piled along the side of the 
trench. The advantages attending the use of machinery are: 
greater amount of material excavated with a given number of 


2y6 


SE WEE A GE. 


men, less danger of caving of banks from the weight of earth 
piled upon them, less obstruction to street traffic, the con¬ 
venience of having at hand means for raising boulders, lower¬ 
ing heavy pipes, or other material. Each of these advantages 
increases in force with the depth of the sewer. With several 
of the machines now on the market the cost of handling 
material increases but little with the depth. The machinery 
in use varies from an ordinary boom-derrick to an elaborate 
system of trestles, wire ropes, and buckets, which may stretch 
along 400 feet or more of trench. 

For a large brick sewer a handy arrangement is that of two 
derricks with booms about 40 feet long, both placed on the 
same side of the trench and about 75 feet apart. Both boom- 
and main-falls should wind upon drums driven by steam- 
power. With this arrangement a bucket of earth can be 
hoisted from the excavation and, passing from one derrick to 
another, be deposited in the trench 125 or even 145 feet 
away. This plan is not adapted to narrow trenches nor to 
those where any considerable length of trench is to be under 
excavation at one time. For these one of the trestle-machines 
or cable-ways is preferable, the former more particularly for 
trenches up to 12 or 15 feet in width, the latter for wider 
ones and for particular cases, such as crossings of railroad- 
tracks. 

The cable-way consists essentially of a wire cable sus¬ 
pended over the centre of the trench, on which run one or 
more travellers carrying buckets; the earth being excavated 
at one point and cast into the buckets, which are raised and 
carried to the other end of the cable, where they dump the 
earth upon the completed sewer. It is essential to the safety 
of the laborers that the cable be most substantially anchored 
at the ends, and that it be amply strong to carry any load 
which can possibly come upon it. The anchorage is usually 
in the shape of a “ dead-man,” but the ordinary log placed 


Plate XII.—Trestle Excavating-machink at Work. 


PRACTICAL SEWER CONSTRUCTION. 


o 


77 





278 


SEWERAGE. 


in the trench and covered with earth back-filling should not 
be relied upon. Rock may be piled in front of and over the 
log, but a better plan is to bury in the trench a platform of 
stout timber, inclined backward about 45 0 from the vertical, 
to which the cable is fastened. The hoisting- and conveying- 
ropes are driven by an engine located at one end of the cable. 
Like derricks, the cable-way is not adapted to trenches which 
move forward rapidly, as the moving and resetting of it take 
considerable time and labor. 

In the trestle-machine the buckets travel upon an over¬ 
head track which is supported at intervals by trestles spanning 
the trench. Generally from 6 to 20 buckets are in use at 
once, one half of which are being filled while the remainder 
are being carried to the dump and emptied. In some ma¬ 
chines the track forms a long.loop, one side of which is for 
going and the other for returning buckets. There are then 
three sets of buckets, one going to the dump, one returning, 
and one set being filled. To obtain the greatest efficiency of 
the machine the number of men casting into each bucket 
should be just sufficient to fill it during the time occupied in 
removing, emptying, and returning a set of buckets. 

Such machinery is economical when the cost of running— 
including all labor but that of the men digging in the trench 
—and of repairs, plus the rental or interest on first cost of the 
machine, is less than the cost of “ staging ” it out (as the use 
of platforms is called) plus that of back-filling. If the back¬ 
filling is to be hand-tamped this last item should not be in¬ 
cluded, since if a machine is used the material must be spread 
after dumping. A good trench-machine is usually economical 
when either depth or breadth of trench exceeds 8 to 10 feet 
in ground capable of rapid trenching; but this economical 
least dimension increases with the decrease in the rapidity of 
excavation possible. Where for some reason the excavation 


PRACTICAL SEWER CONSTRUCTION . 279 

can proceed but slowly the use of machinery is not advisable 
for economical, though it may be for other, reasons. 

Whatever the machinery employed it should work suc¬ 
cessfully although the sheathing extend at least 6 feet above 
the surface along each side of the trench, should be able to 
drop a bucket anywhere in the trench, each bucket being 
always under perfect control, and no cable or rope should 
hang within 6 feet of the ground. It is better that it should 
have no cross-ties or other parts extending across the trench 
within 6 feet of the ground, and that it should not obstruct 
the street for more than 2 feet on each side of the trench. 

For deep trenching through city streets the use of exca- 
vating-machinery is strongly recommended as of advantage to 
both city and contractor. 

Most makes of excavating-machinery can be either rented 
or bought. For a village or small city the former is generally 
preferable if the work on which it is to be used can be pushed. 
But if it will be needed for more than one season it may be 
preferable to buy instead. 

Probably the best-known and most extensively used 
trenching-machinery are the Carson, of Boston, Mass., and 
the Moore, of Buffalo, N. Y. Other machines are described 
in Engineering Record, vol. XVI, page 123, vol. XXXIII, page 
100; and in Engineering News, vol. XXIV, page 268, vol. 
xxv, page 547, vol. xxxvn, page 50. 

Art. 72. Sheathing. 

Just when a trench can be relied upon to stand without 
sheathing and when it cannot is something that only experi¬ 
ence can teach. Sheathing is expensive, but not so expensive 
as excavating a trench which has begun to cave, to say noth¬ 
ing of settling for injuries and death of laborers. If earth has 
been piled upon a bank which afterwards caves it may be 



28 o 


SEWERAGE. 


necessary to re-excavate more material than all that which 
would have been excavated had no caving occurred, and all 
of this must be removed to some distance because there is no 
bank upon which to pile it. Not only that, but the soil is 
liable to continue to slide into the trench, making it almost 
impossible to keep the bottom uncovered. If, after caving 
has begun, sheathing is used the difficulty of placing it is 
greatly increased. A trench which if sheathed would have 
given no trouble may become a most discouraging hole into 
which many times the cost of sheathing must be placed in the 
form of labor before the sewer is built therein. The author’s 
experience has been that it does not pay to take many 
chances with unsheathed trenches. He would use at least 
skeleton sheathing in every trench more than 8 or io feet 
deep, in any trench in gravelly and sandy soil, and whenever 
the least sign of caving appears. Wherever the street is paved 
a plank should be placed horizontally on each side of the 
trench about 6 inches below the surface, and braces driven 
between these not more than 6 feet apart. 

Sheathing is usually placed as follows: A plank ( a , Fig. 
13) is placed upright in the trench against the bank, another 
( b ) 12 feet from this, and two against the other bank and 
directly opposite these. Against each two and near the 
street-surface is placed a horizontal ranger (cd and ef), both 
at the same level, and between them at each end a brace is 
driven, long enough to be a tight fit. Two other rangers (gk 
and kl) are placed, one on each side of the trench, from 4 to 
6 feet below the others, and braced. Sometimes these lower 
rangers are placed first. The ends of the rangers come in the 
middle of the uprights, the braces only an inch or two from 
the ends of the rangers. The next set of rangers abut against 
these and are braced in the same way. Generally an addi¬ 
tional upright and braces are placed midway of each ranger. 
This forms skeleton sheathing. 


PRACTICAL SEWER CONSTRUCTION. 281 

If the sheathing is to be close, plank are slipped behind 
the rangers and in contact with each other, and one or more 
additional braces are placed at equal intervals between each 
tier of rangers. For bracing only, the rangers and braces are 
used without any vertical sheathing. These are ordinarily 
placed a foot or two from the surface, or just beneath and in 



front of an exposed water-main or other conduit. When a 
series of rangers and braces are placed one just below the 
other horizontal sheathing is formed. 

As the trench is deepened the sheathing should be driven 
so that its lower end is as near as possible to the bottom of 
the trench, unless rock or some firm soil be previously 
reached. In quicksand or running sand the bottom of the 
sheathing should always be kept at least one foot below the 
bottom of the excavation . This is essential if the work is to 
be done without considerable loss of money and perhaps of 
life. As many men as are necessary to insure this should be 
kept constantly at work driving the sheathing. No two planks 
behind the same ranger should be driven at once, as the latter 
would in that case be apt to follow them down, which it 
should not do. 

If there is a tendency for the sheathing to be forced in at 




































282 


SE WEE A GE. 


the bottom by the bank, as in the case of quick or running 
sand, a set of rangers and braces should be put in place im¬ 
mediately under the lowest set already in position as soon as 
the excavation is low enough to permit it. As the excavation 
and sheathing are carried down this last set of rangers should 
be driven down, always being kept level crosswise of the 
trench and just above its bottom, until it is the proper dis¬ 
tance below the preceding set, when it is driven no further, 
but another set is started under it. If the bank is tolerably 
stable the stiffness of the sheathing-plank can be relied upon 
to keep it in place below the second ranger until the trench 
is sufficiently deep to permit placing the third ranger in its 
proper position without any further driving. 

Each brace should be exactly beneath the braces in the 
tiers above. 

There is considerable friction between the sheathing and 
the bank on one side and rangers on the other, and after two 
sets of rangers are in the driving becomes quite difficult and 
the upper ends of the plank become battered and broomed 
and the plank broken, sometimes even when they are pro¬ 
tected by caps. Ordinarily io or 12 feet is the greatest depth 
to which plank can be driven economically. It then becomes 
necessary to start a new course of sheathing, which is placed 
inside the upper course, its back resting against the rangers 
of this. The second course is driven and held in place by 
rangers and braces as was the other, and may be succeeded 
by one or more other courses each io or 12 feet high. When 
a new course of sheathing is started it is advisable to tem¬ 
porarily fasten planks horizontally in front of and behind this 
sheathing near the top, by a nail at each end driven into a 
sheathing-plank, to keep the plank in line and steady them 
while driving. 

In placing each course after the first one an opening must 
be left at each vertical line of braces, since the sheathing 


PRACTICAL STIVER CONSTRUCTION. 283 

cannot be driven there. If these openings give trouble they 
may be closed by slipping into them, behind the rangers, 
5-foot lengths of plank when the trench has reached that dis¬ 
tance below the first course of sheathing, and driving these 
to keep pace with the other sheathing. When the trench is 
5 feet deeper still another 5-foot length of plank may be 
slipped behind the ranger on top of the former length, and 
so on. A short piece of plank, at least, should be kept in 
the bottom of this opening to keep the planks on either side 
the proper distance apart. 

Another method of closing these openings is to cut a plank 
just long enough to reach from the bottom of one ranger to 



Fig. 14.—Sheathing under Braces. 

the top of the next and a little wider than the opening. 
This is placed over the opening against the face of the sheath¬ 
ing, and between the rangers, to which blocks are nailed to 
hold it in this position (see Fig. 14). 

In some cases it will not do to leave this space open for 
even a foot above the bottom of the trench, as in quicksand. 
It may then be advisable to use a somewhat different system 
of rangers, as follows: In placing rangers for the first course 
of sheathing, where one ranger is ordinarily placed two will 
be placed, one in front of the other but separated from it by 
a small piece of plank at the end of each brace. The front 
ranger may be but a 2-inch plank. The second course of 



























































284 


SE WEE A GE. 


sheathing is slipped between the two rangers and when it is 
all in place except where the spacing-blocks interfere the 
braces are driven along about a foot, the spacing-blocks 
knocked out, and sheathing dropped into the spaces they 
occupied. Generally plank behind a brace cannot be driven, 
owing to the friction, but when the one next to it has been 
driven the brace can be moved over in front of this and the 
former then driven. 

Where there is more than one course of sheathing, or 
whenever the bottom of any course is not kept at the bottom 
of the trench, all braces in each vertical line should be tied 
together by cross-bracing of plank nailed to them; otherwise 
one side of the sheathing may drop, loosening the braces and 
causing a complete collapse of sheathing and trench. The 
author has seen several serious accidents due to the neglect 
to use such cross-bracing. 

The sheathing is usually of hemlock plank, although pine 
would be better, being less brittle. Maple and other hard 
wood has been used in a few instances. The plank is usually 
2 inches thick, although heavier may be advisable in deep, 
wide trenches or where it is desirable to use as few rangers 
and braces as possible. It should never be less than 2 inches 
thick. Ten or 12 feet is the usual length, although 18 or more 
is sometimes used. But the great amount of friction between 
such long plank and the earth makes it extremely difficult to 
drive the last 6 or 8 feet, the top of the plank being usually 
broomed or broken in the attempt. For the same reason the 
width of the plank does not usually exceed 6 or 8 inches. 
All the sheathing in a given course should be of approxi¬ 
mately the same length. Sheathing-plank should be sharp¬ 
ened to a chisel edge, the flat side being placed against the 
bank, and the edge which will not be in contact with the 
plank last driven should be bevelled, that the plank may hug 
the bank and keep a close joint with the one previously 


285 


PRACTICAL SEWER CONSTRUCTION. 


driven. The bevel may be 3 to 5 inches long. The top of 
the sheathing-plank should be bevelled on each edge, to 
lessen splitting and binding and to permit of using a driving- 
cap, which is advisable if the sheathing drives hard, to keep 
the plank from brooming. 

For driving the sheathing a hardwood maul is ordinarily 



Fig. 15.—Driving-cap and Maul. 


used, about 6 inches in diameter and 15 inches long, with a 
wrought-iron hoop banding each end. 

If a large amount of sheathing is to be driven in deep 
trenches a steam-hammer pile-driver may be used to advan¬ 
tage. This does not broom the pile, and by using it sheath¬ 
ing 18 feet long or more may be driven. It is particularly 
applicable to sand and elastic soils. 

If the ground is such as to require sheathing from the 



very beginning of the excavation it would be difficult to keep 
vertical sheathing standing and in line while the trench is only 
I to 3 feet deep, and it would greatly interfere with casting; 



















































































286 


SEWERAGE. 




out the excavated material. It will be better in such a 
case to erect skeleton sheathing, with only one set of rangers 
and braces and short uprights, behind the uprights placing 
plank laid horizontally. When this construction has been 
carried down 5 or 6 feet vertical sheathing can be started 
and continued as above. But even then if the vertical 
sheathing is more than 8 feet long it will be necessary to use 
platforms or staging, unless a sheathing-plank can be omitted 
every 5 or 6 feet and the earth cast out through the open¬ 
ing thus left. On account of the difficulties just described it 
is better, if the trench is so deep as to require more than 
one course of sheathing, to place shorter sheathing in the top 
course—for instance, 6-foot sheathing and then 12-foot in a 
15- to 18-foot trench. 

Some contractors use horizontal sheathing altogether, the 
verticals being only 3 or 4 feet long, several being placed one 
above the other. Most American contractors, however, 
prefer the vertical sheathing. 

The size of the rangers may vary between wide limits, but 
in any one trench they should all be the same length, and 
when in position the ends of all should come opposite or 
under each other. Two-inch plank may be used for rangers in 
ordinary loamy or clayey soil and shallow trenches, and the 
braces placed with sufficient frequency to prevent their belly¬ 
ing too much. This would in many cases bring the braces so 
close to each other as to interfere with the work, and it will 
then be advisable to use 4X4 or 4X6 material. The 
author prefers these in any case, as being stronger, but neither 
costing nor weighing more, than 2-inch plank. If excavating- 
machinery is used the braces should be at least 5 or 6 feet 
apart, and the rangers of 4X6 or 6x8 timber. The 
deeper the trench the heavier should be the rangers and 
braces. 

The braces should be heavier also the wider the trench, 







PRACTICAL SEWER CONSTRUCTION. 2 87 

since they must act as posts. They are often, for conve¬ 
nience, made of the same size of timber as that used for 
rangers. Each brace must be fitted to its place, since the 
width of a trench usually varies at different points within a 
range of several inches. For finding the length of brace 



Fig. 17.—Sliding Rod for Measuring Braces. 
required it is handier to use a sliding rod than a measuring- 
rule. The brace should be made a little longer than the dis¬ 
tance between rangers, that it may drive hard into place and 
fit there tightly. To make this driving easier one edge of 
one end of the brace may be slightly bevelled. 

Instead of wooden braces extensible iron ones are coming 
into general use, and for narrow trenches at least are equally 
as good and much more convenient, since they can be quickly 
adjusted to any position and used over and over again. For 
wide trenches those in the market are hardly stiff enough, but 
are apt to buckle under extreme pressure. Trussed beams, 
however, can be obtained with extensible ends, which meet 
this objection. If much bracing is to be done the cost of 
extensible braces can be saved in the carpenters’ wages many 
times over. 

Much heavier sheathing than here described may be 
necessary in deep trenches in some soils. In stiff marsh-land 
near New York City, in a trench 26 feet wide and 25 feet 
deep, 6-inch sheathing was found necessary, with 10 X 10 
rangers and 8X8 braces 5 feet apart horizontally and 
vertically. 

In cases where the soil was soft round piles have been 
driven a few feet apart along the side lines of the trench before 

1 

excavation, and as this proceeded horizontal sheathing was 
inserted behind the piles and braces placed across the trench 
between them. 


1 









288 


SEWERAGE. 


The rangers and braces can be used over and over again if 
they are not left in the trench; the sheathing, too, can 
ordinarily be used several times; but each time a set is used 
a few plank will probably be broken, either in driving or in 
drawing. As stated in connection with Table No. 2 1, good 
sheathing can ordinarily be used two to five times, taking an 
average of all used at the outset. 

In many instances it is desirable to leave the sheathing 
in the trench, sometimes with and sometimes without the 
rangers and braces. The conditions calling for leaving in 
sheathing are: that drawing it may endanger the sewer, or 
water- or gas-pipes in the street near the trench, or adjacent 
buildings, or that the street-paving will be injured thereby. 
The danger to buildings usually exists only in connection with 
deep trenches in unstable soil or where a building is quite 
near a sewer which lies below its foundation. Water- or gas- 
mains would be endangered if within two or three feet of, and 
more than that distance above the bottom of, a sewer-trench 
in fairly good soil. If the soil has shown a tendency to crack 
along the banks near the trench the sheathing should not be 
drawn if the street is well paved; and if water- or gas-pipe or 
other sewers are laid in such street the judgment of the 
engineer must decide at what distance they may be consid¬ 
ered safe from disturbance if the sheathing be drawn. If the 
sheathing has been driven below the centre of a sewer, as 
must be done under some conditions, its removal would dis¬ 
turb the foundation of the sewer and should not be attempted. 
But if two or more courses of sheathing have been driven 
all but the lowest course may be removed if the sewer only 
is affected. The rangers and braces as well as the plank should 
usually be left in. If the banks are liable to cave with the 
drawing of the sheathing the trench should be filled to a dis¬ 
tance above the sewer at least equal to its width before the top 
braces are knocked out or any sheathing-plank is entirely drawn. 


PR A C TIC A L SE WER CONS TR UC TION. 289 

Before drawing sheathing the back-filling, if it is not to be 
rammed, should be carried to a point at least 3 feet above 
the bottom of the plank. The bottom set of braces and 
rangers may then be removed. If this gives less than 2 feet of 
back-filling above the top of the sewer this amount should be 
thrown in and properly tamped. When the sewer is properly 
covered the remaining braces and rangers may be removed 
and the sheathing entirely drawn. If the bank should cave 
badly on the removal of the braces it might break the sheath¬ 
ing, and in such a case it may be better to continue back¬ 
filling and slowly drawing the sheathing, each set of rangers 
being removed only as the back-filling reaches them. If there 
is more than one course of sheathing this plan should be fol¬ 
lowed in every case with all but the top course, unless the 
others are to be left in the trench, which may be cheaper in 
some cases. 

Drawing the sheathing is often a difficult matter if only 
the hands or a pick be used. A convenient plan is to use a 
sheathing-puller, made of iron \\ or 2 inches thick and 3 or 



4 inches wide. The ring on the clamp should be so placed 
that the clamp will slide down the sheathing when not sup¬ 
ported, remaining constantly horizontal. After placing this 
in position on a horse a simple pump-handle motion with 
the lever will suffice to draw the plank. A chain to be 
hooked tightly around a sheathing-plank may be used as a 
substitute for the clamp, but is not convenient for close 


























290 


SE WEE A GE. 


sheathing, which must be pried apart to admit it. Better 
than this sheathing puller, where excavating-machinery is 
being used, is to use the engine-power to draw the sheath¬ 
ing by fastening the clamp to a hoisting-rope. 

Where a building is so situated with reference to the 
sewer-trench that its stability is endangered thereby the 
greatest care should be taken with the sheathing to prevent 
any material behind it from caving into or in any way enter¬ 
ing the trench. To insure this the sheathing-plank must 
be tight together—in sand it may be necessary to use tongued 
and grooved plank—and their bottoms should be kept well 
below the bottom of the trench. If this is done and the 
bracing is strong and stiff there should be little danger, unless 
the material is semi-fluid, when it may be impossible to pre¬ 
vent a settlement of the ground and buildings, unless by 
freezing the soil by the Poetsch process (an exceedingly 
expensive one) or some similar method. 

If a settlement of a portion of a building-foundation seems 
probable the building should be shored and jacked up. One 
method of accomplishing this is to make openings just above 

m 

the ground-surface 6 to 10 feet apart and of a size to permit 
large beams—10 X 12, or 12 X 14 or 18—to be passed through 
them. These beams are supported at each end by jacks, 
which in turn rest upon blocking placed upon the ground. A 
careful watch is kept of these and at the least sign of settle¬ 
ment of the ground the jack above is screwed up an amount 
equal to this settlement. As a further precaution it may be 
advisable to shore up the walls by a sufficient number of heavy 
timbers, whose lower ends are supported upon platforms or 
grillage, wedges being placed under the foot of each and 
driven up when necessary to make up any settlement of the 
ground. The shores at their upper ends bear against beams 
bolted to the walls of the building, or in masonry walls are 
received by openings about a foot deep cut therein. Shores 


PRACTICAL SEWER CONSTRUCTION. 291 

alone are often employed when the building is not valuable 
or the danger is small. 

Art. 73 . Laying Sewer-pipe. 

It will save considerable trouble in the laying of pipe if 
the foreman has the trench dug exactly to line and grade as 
ascertained by measuring and plumbing from a grade-line 
already set. It is better to have the bottom a little too high 
rather than too low. 

Pipe sewer is usually laid up the grade, and the pipes are 
so manufactured that the specials must be laid with their bell 
ends pointing up. Laying the sewer-pipe in this way is more 
likely to produce good joints, particularly if the grade is at 
all steep, since if laid down grade a pipe, after being placed 
in position and before the next is laid, tends to slide away 
from the one next above it and cause a break in the inner 
surface of the sewer and a leaky joint. It is also much easier 
to lay pipe with the bell pointing ahead, and the cement joint 
is apt to be firmer. The only reason advanced for laying pipe 
down hill is that the lower end of the trench being ahead of 
the pipe, any ground-water will be kept drained away from 
the sewer construction. This is discussed in Art. 78. 

For lowering into the trench pipe which does not weigh 
more than 100 pounds a convenient method is to use a rope 
of f to i£ inch diameter with a hook at one end. The hook 
is passed through the pipe from spigot to bell and then back 
over the outside to the middle of the pipe and caught on the 
rope there, so that the pipe when suspended will be horizon¬ 
tal. Or the hook may pass through the pipe from bell to 
spigot and be simply caught over the end of the latter. The 
pipe is lowered over the edge of the trench by one man and 
received at the bottom by another if light, or by two if 
heavy, the hook being unfastened and pulled up. If the pipe 
weighs more than ioo pounds two men will be required to 


292 


SE WEE A GE. 


lower it, which they do by each holding one end of a rope 
which passes through it. For pipe heavier than 200 pounds 
it is advisable to use an ordinary three-leg derrick with light 
tackle-block. The pipe is then suspended by a rope or chain, 
with a hook at one end and a ring at the other, passed through 
the pipe and so hooked that it may be lowered in a horizon¬ 
tal position. A convenient arrangement for holding the pipe 

consists of a hook (Fig. 19), which should 
be at least two thirds the length of the 



3 


^ .wwww^ pipe and very strong at the bend. The 
ring must come beyond the centre of 
gravity of the pipe to prevent its falling off 
the hook. By use of this a pipe can 
while suspended be entered into the bell 




Fig. 19.—Pipe-laying of the one previously laid and much heavy 
Hook * lifting by hand avoided. 

Another method of entering heavy pipe after it is in the 
trench is sufficiently explained by the illustration Fig. 20. 



Fig. 20.—Appliance for “Entering” Heavy Pipe. 


This is made of wood or iron, with a loose wheel on either 
side of the bar at the bottom. 

Before a pipe is lowered into the trench a “ bell-hole” 
should be dug where its bell will come, of such size that when 
the pipe is in position the jointer can pass his hand entirely 
under and around the front of the bell. It is convenient to 














































PRACTICAL SEWER CONSTRUCTION. 


293 


have a stick exactly as long as two or three lengths of pipe, 
by which the location of each bell-hole is measured from pipe 
already laid, the bell-holes being dug for a few lengths in 
advance of the sewer. 

Two men should be employed in laying sewer-pipe, one 
straddling the pipe last laid, the other in the trench just 
ahead of it. The latter as the pipe is lowered guides it into 
place and releases the hook on the lowering-rope, if one is 
used. The former, holding one end of a length of packing in 
each hand, places the loop thus formed under and around the 
pipe about an inch from the spigot end and guides this into 
the bell of the pipe last laid, taking care that the packing also 
enters the bell. With a yarning-iron he then pushes the 
packing up against the shoulder of the bell all around, being 
first sure that the pipe is “ home ” in the bell. The other 
pipe-layer meantime supports the pipe at the bell end and 
shoves it home. The grade-rod and plumb-bob are then 
used. If the bell end is too high (the spigot end should be 
all right, since the previous pipe is) it may, if the soil is 
loam or loose clay or sand, be forced down a quarter of an 
inch, more or less, by standing and jumping upon the top of 
the pipe. (The pipe-layer should never rest his foot inside 
the pipe to force it down, as this is likely to break the bell or 
even the pipe.) If the soil is stiff clay or gravel the pipe 
should be removed and the trench bottom lowered sufficiently 
with the shovel. If the pipe is too low it should not be raised 
by placing a stone or piece of wood under it, but should be 
removed and fine earth placed and rammed in the bottom of 
the trench. By means of the plumb-bob the pipe should be 
centred exactly under the grade-line. A convenient way of 
doing this is to suspend the bob from the cord at a grade- 
plank, being careful not to lower the cord by its weight; 
then, when the eye is so placed that the cord and plumb-bob 
string coincide, the former is projected by the eye vertically 


294 


SEWERAGE. 


into the trench and should cut the centre of the pipe. With 
a circular salt-glazed pipe the centre is known by a streak of 
light reflected from the sky, and this streak should be bisected 
by the vertical projection of the grade-cord. Another plan 
for obtaining a vertical projection of the grade-cord is to 
stretch another cord a foot or two vertically below it. But 
this method is less accurate in practice than the other and is 
not recommended. The grade-cord cannot be stretched so 
tight that it will not sag T x ^ to J of an inch at the centre, but 
allowance may be made for this in using the grade-rod. The 
foreman or inspector who uses the grade-rod will need to have 
a short movable plank spanning the trench just ahead of the 
pipe being laid, on which to stand. 

As soon as a pipe is in position sufficient earth should be 
placed and rammed on each side of it just back of the bell to 
prevent its moving. The next pipe is then lowered and set, 
and so on. 

At least two joints behind the pipe which is being set is 
another man, who cements the joints. The cement he usually 
keeps in an iron pail of ordinary size (although one having 
the shape of a pan would be better), just enough being mixed 
at a time to permit his using it all before it stiffens. If there 
is any delay in laying the pipe the pail should be cleaned out 
lest the cement set in it. The jointer should wear rubber 
mittens, and a small trowel will be found more convenient 
than the fingers for getting the cement out of the pail. The 
cement mortar should ordinarily be about as stiff as putty, 
but if the trench is wet it should be as dry as it can be and 
have any cohesion. The jointer takes a handful of mortar in 
each hand and presses it into the bell all around, drawing his 
hands meantime around the joint. With a wooden or iron 
calking-tool he compacts the cement in the joint, adding 

more as is necessary, and with additional mortar he makes a 

/ 

neat bevel outside the bell, continually pressing the mortar 



PRACTICAL SEWER CONSTRUCTION . 


295 


firmly towards the bell. This bevel should not be flatter than 
45 0 , since if too much mortar be outside the bell its weight 
may cause it to fall away from the pipe and perhaps draw 
with it the mortar from inside the bell. The compacting of 
the cement is frequently omitted, but is necessary if tight 
joints are to be obtained. 

Just behind the jointer should be another man, who, as 
soon as a joint is made, fills the bell-hole carefully with fine 
earth well tamped, and then fills and tamps the same material 
under and around the rest of the pipe up to at least its 
middle. His tamping-bar should be of wood, there being 
danger of breaking the pipe if the ordinary iron ones are used, 
and with a face about 2X4 inches. If the trench is wet so 
that water collects in the bell-holes the mortar is likely to 
become softened and fall out of the joint. To prevent this a 
piece of cheese-cloth may be wrapped tightly around the joint 
after it is made, as specified for sub-drains; or the bell-hole 
may be immediately filled with concrete thoroughly com¬ 
pacted. The latter is the better but more expensive plan. 
Where there is much water in the trench it is strongly recom¬ 
mended that concrete be placed not only in the bell-holes but 
entirely around the pipe at the joints (see Art. 46). 

In making the joint it is quite probable that some cement 

will be squeezed into the pipe, forming a ridge or lumps on 

the inside. To remove these a bag or disk should be drawn 

through the pipe past the joint as soon as it is finished, which 

is done by the pipe-layers. The bag may be an ordinary 

cement or similar sack, somewhat larger than 

the sewer, filled with straw or excelsior and a 

rope tied around its mouth and carried through 

the sewer, being passed through each pipe as 

it is laid. The bag should fit snugly against Fig - 21.—Pipe¬ 
cleaning Disk. 

the pipe all around.. Instead of the bag a 

disk of heavy rubber packing bolted between two smaller 








296 


SE WEE A GE . 


wooden disks and fastened to an iron rod may be used, being 
drawn forward as in the case of the bag. The rubber disk 
should be slightly larger than the sewer. 

When a manhole or other break in the sewer is reached in 
the pipe-laying the last pipe before reaching and the first 
after leaving it should be omitted or left with uncemented 
joint, to be laid while the manhole or other appurtenance is 
being built. This is on account of the probability of such 
pipe being disturbed or broken during the construction of the 
masonry before it has been walled in. In this or any case 
where a stretch of pipe ends, or when the laying is temporarily 
stopped, a plug should be inserted in the end of the last pipe, 
and a bar or stake driven against it into the ground or nailed 
to the sheathing to hold it in position. The last joint should 
be left uncemented until laying is renewed. 

In setting branch specials the earth where the special will 
come should be so excavated as to permit the branch to rest 
upon it firmly when in the desired position. If necessary 
earth should be placed and tamped under the branch for this 
purpose. The inspector must not forget to examine each 
branch to see that a cover is cemented in it, unless the house- 
connection is to be built at once, and also to mark its location. 
In wet soil particularly uncovered branches may give rise to 
serious difficulty, and an unlocated branch is worse than none 
at all. 

If work must be done in the winter-time great care should 
be taken to prevent the mortar from freezing and to keep ice 
and frozen dirt out of the joints. In pipe-joints this is not 
very difficult if the trenches are at all deep, since in these the 
temperature seldom falls below 40°. But the sand for mortar 
should be heated, and the pipe also, to insure the removal of 
all frost from the bells and spigots. In shallow trenches the 
joints should be covered as soon as possible with at least two 
feet of unfrozen earth. Care should be taken, particularly 


PRACTICAL SEWER CONSTRUCTION. 297 

when back-filling is dumped from excavator-buckets, that no 
frozen lumps fall upon the sewer. 

The back-filling of trenches has been sufficiently discussed 
in Art. 54. When this is thrown in without ramming particu¬ 
lar care should be taken that all pipe be first well covered with 
earth, since stones and frozen lumps invariably roll to the foot 
of the face-slope of the back-filling and might crack unpro¬ 
tected pipe. 

It is frequently necessary to cut a sewer-pipe to a certain 
length or to split one in two to obtain a channel for a man¬ 
hole bottom. This can be done with a cold-chisel and 
hammer, a light cut being made first entirely around or along 
the pipe and this gradually deepened until the pipe of itself 
breaks in two. The pipe is sometimes filled with sand well 
packed before the cutting is begun, but this is not necessary 
if care be used. 

Art. 74 . Building Masonry Sewers. 

Circular or egg-shaped masonry sewers may consist of a 
ring of masonry of uniform thickness throughout, or this ring 
may be much thicker in the arch than in the invert, or there 
may be invert-backing masonry resting upon a platform foun¬ 
dation or filling the irregular spaces of a rock cut. If the 
sewer comes under either of the first two cases it is usually 
made entirely of either brick or concrete, owing to the 
expense of dressing stone to make tight work in compara¬ 
tively thin rings and to give a smooth interior surface. For 
massive masonry, as in invert-backing or heavy arches, stone 
can be used and is in many cases cheaper than brick. In some 
instances concrete may be cheaper and better than either. 

A simple ring invert can be used only where the soil is 
firm and compact enough to stand when given the shape of 
the outside of the invert; such as clay, pure or mixed with 
sand or loam. If it will not retain this shape while the sewer 


SEWERAGE. 


298 


is being built, but is solid enough to offer good foundation, 
as damp sand, the bottom of the trench may be given a flatter 
curve and lined with a board or plank cradle, upon which 
concrete or stone masonry is placed for the invert-backing, to 
be lined with 4 inches of brick-work. In rock cuts the same 
plan may be adopted, since it is usually impracticable to bring 
the rock to the exact shape of the sewer (see Plate VI, Fig. 
10). 

If artificial foundation is necessary this usually consists of 
a platform, upon which the masonry rests, and which is placed 
directly upon the trench bottom or supported upon piles. 

If the arch is of such dimensions that the thrust is more 
than the banks can be trusted to sustain, and a shape similar 
to that shown in Plate VI, Fig. 5 or 9, is adopted, concrete 
or stone masonry may be used for the side walls, and a plat¬ 
form is generally necessary for foundation except in a rock 
trench. 

Where no invert-backing is necessary the method usually 
employed is as follows: Templets, two for each gang of 
masons, are provided conforming to both the inside and 
outside shape of the sewer. A convenient form is shown in 
Fig. 22, which is for two rings of brick. This is made of 





Fig. 22.—Templet for Brick Sewers. 


boards or plank, 2-inch plank being sufficiently heavy for any 
but very large sewers. A templet for an egg-shaped sewer 
can of course be made in the same way. Each ring of brick 








PRACTICAL SEWER CONSTRUCTION. 299 

is represented in the templet by a layer of plank, its inside 
edge conforming to the inner surface of said ring. A number 
of fourpenny or fivepenny nails are driven along the edge of 
each plank at equal intervals, the space between them being 
the thickness of a brick plus that of the mortar-joint, usually 
about 2 \ inches. Each templet should be an exact duplicate 
of the other, including the position of the nails. At the exact 
centre A of the cross-piece a notch is cut or a nail driven. 

When the bottom of the trench is about to grade one of 
these templets is set in a vertical position so that the centre 
of the cross-piece is exactly in the centre line of the sewer, 
the cross-piece level, and the inside of the templet at the 
proper grade for the sewer-invert. About 12 to 20 feet along 
the trench the other templet is similarly set, the sides of the 
templets containing the nails facing each other. If now a 
cord is stretched from any nail in one templet to a correspond¬ 
ing nail in the other the excavation should be exactly the 
same distance outside this as is the outside of the templet. 
If the excavation should be carried too far it must be filled 
with sand well rammed, or with good cement mortar. 

The cord is now stretched between the lowest nails in the 

\ 

outer rings of the two templets, and the brick laid to this line 
from end to end. The cord is now shifted to the next nail 
in the same ring and the next row of brick laid. When two 
or three courses have been laid on one side of the centre the 
same number are laid on the other side, and both sides of the 
sewer are carried up simultaneously, for which reason the 
masons usually work in gangs of 2, 4, 6, or 8. Not more 
than the last number can work to advantage on one section of 
invert, but several sections may be under construction simul¬ 
taneously. 

When four or five courses have been laid a plank is placed 
on these for the masons to stand on, and the brick-work is 
continued row by row, each row being laid carefully to line. 


3oo 


SE WEE A GE. 


The bricks of succeeding courses should break joints at least 
3 inches. 

After the outer ring has been completed to the springing- 
line the next is laid in the same way. The bricks of each 
ring should be bedded in mortar at least ■§■ inch thick, and 
every joint should be completely filled. Considerable diffi¬ 
culty will be found in getting any but experienced sewer- 
masons to lay the brick radially, but smooth work cannot be 
obtained otherwise and this must be insisted upon. All 
joints should be carefully struck. If they are not they should 
be afterward raked out and pointed. 

If the brick do not absorb more than 2 or 3 per cent of 
water in the absorption test they should not be wet, as they 
cannot then be made to stay in place. But if they take more 
water than this they should be wet just before using. A 
quick test for this on the ground is to drop a brick into 
mortar and remove it. If the mortar does not in two or 
three minutes grow dry where it touches the brick they prob¬ 
ably do not need wetting. 

The mortar is usually mixed in a box on the bank (it 
should never be mixed on the ground for any purpose) and 
lowered into the trench in a pail by a rope provided with a 
hook, where it is emptied onto the mortar-boards. These 
boards are usually 24 to 30 inches square. The brick is 

placed in hods on the bank and lowered to the 
masons. A convenient form of hod is shown 
by Fig. 23, which is made of sheet iron and 
can be quickly filled and emptied. The ma¬ 
terial is usually lowered by hand for small 
sewers, and the man who does this should 
have a heavy leather palm-piece for each hand. 
Fig. 23.— Hod FOR A leather glove or mitten would not last a 
Lowering Brick, day of hard usage at such work. To permit 
of lowering the material a platform is usually thrown across 






PRACTICAL SEWER CONSTRUCTION. 301 

th^ trench above where the masons are working. If stone is 
being laid, or much material is to be used at one place, or the 
trench is quite deep, the material may be lowered by a wind¬ 
lass set in a portable frame or by a derrick. If excavating- 
machinery is being used this may be utilized for lowering the 
material. 

As the invert of the sewer rises it becomes difficult for the 
masons to lay the brick, and the material if in the bottom of 
the sewer is too far from the work. A platform is then 
necessary and can be made by sawing plank of such length as 
to be at the desired elevation when placed horizontally cross¬ 
wise of the sewer. Three or four of these can be thus laid, 
with a few brick under the centre of each as additional support, 



Fig. 24.—Masons’ Platform for Brick Sewers. 

and a platform of loose plank placed over them. But this is 
apt to distort the green brick-work at the ends of the cross¬ 
plank, and it is better to have a number of plank cut to the 
shape of the sewer-invert cross-section, which will distribute 
the load along their entire length, and to rest the platform 
on these (see Fig. 24). 

When one section of invert is completed one of the 
templets is moved ahead the length of a section and set. The 
other will not be needed by the masons, since one end of the 
cord will be fastened to nails stuck into the joints of the 
invert just completed. The second templet can, however, be 
used to advantage for grading the trench ahead of the masons. 

In bonding the new work with that previously laid (the 












302 


SE WEE A GE . 


end of which should be toothed or racked back) all loose 
brick and mortar should be removed, and the brick cleaned 
and wetted before applying fresh mortar. 

The arch of the sewer is built upon a “ centre/' which is 
removed when the arch is completed and the mortar suffi¬ 



ciently set. The centre usually consists of lagging supported 
by curved ribs of wood or iron. Probably the most common 
form is that shown in Fig. 25. To templets similar in form 
and general construction to those for the invert are nailed 
lagging-strips about 1 inch thick and i-| inches wide, spaced 
2 \ inches between centres, there being a templet at each end 
and intermediate ones spaced 3 or 4 feet apart. The lagging- 
pieces should be perfectly parallel, as their edges are used for 
lining the brick-work. If the radius of the arch exceeds 2 
or 3 feet the lagging may be of i£- or 2-inch by 3^-inch 
strips, spaced 4J inches between centres; but the 2j-inch 
spacing will give a better surface whatever the radius. The 
templets should lack 3 or 4 inches of being complete semi¬ 
circles, so that when in position the bottom of the centre may 
be about i-J or 2 inches above the springing-line of the arch. 
The centre may be held in position by a triangular frame 
under each templet, supporting a plank along each side of the 
sewer, upon which the centre rests, it being raised to exact 
position by wedges, as shown in Fig. 25. When the arch is 

















PRACTICAL SEWER CONSTRUCTION. 303 

completed the wedges are knocked out and the centre drops 
onto the two planks and can be pulled forward, sliding upon 
these. It is sometimes difficult, particularly with large and 
heavy centres, to draw them out, and to facilitate this a light 
temporary track has in some instances been built under the 
centre, which was placed upon wheels which rose 2 or 3 
inches above the track when the centre was wedged up into 
position. By knocking out the wedges the centre drops onto 
the track and can be readily rolled forward. The use of rings 
of angle-iron to support the lagging gave good satisfaction in 
Denver, Col. (see Transactions of Am. Soc. Civil Engineers, 
vol. XXXV, page 113). For very large sewers it may be better 
to build each centre in place and take it apart in order to 
move it. 

The arch should be built up at a uniform rate on both 
sides at once, and the last row of brick to be laid in each ring 
should be at the crown and should be driven tightly into place 
as a key. It may be necessary to split brick for this purpose, 
but it is better to have on hand a number of thin arch-brick 
(of wedge-shaped section), hard and tough, which will stand 
driving. The outside of the arch is usually plastered with \ 
to i inch of mortar. The centre should be left under until 
the mortar is so set that there is no danger of the arch 
becoming deformed if it is drawn, the time varying with the 
character of cement, shape and thickness of the arch, and 
other details of construction. It is probably well in most 
cases to back-fill to the crown of the arch as soon as it is com¬ 
pleted. But if the soil is wet, like muck, or if, when excavat- 
ing-machinery is used, the buckets usually contain consider¬ 
able water, no back-filling should be done until the mortar is 
thoroughly set. 

If the arch is of stone or concrete masonry lined with 
brick the brick ring is laid as described above and the stone 
or concrete built on top of it. The arch is sometimes built 


304 


SEWERAGE. 


of concrete without a lining, in which case the lagging-strips 
must be set close together. In the Wachusett (concrete) 
Aqueduct, 11 feet 6 inches in diameter, sheets of galvanized 
iron and zinc greased with black-oil were fastened over the 
lagging on the centres with good results. 

After the removal of the centre the arch masonry will 
ordinarily be found somewhat uneven, with mortar adhering 
in flat lumps to a large part of its surface. These should be 
removed and the joints so pointed as to render the surface 
more even, or the whole inside of the arch may be plastered. 

If there is masonry backing to the invert this is usually 
laid as uncoursed rubble or concrete up to within 4J inches 
of the invert-surface, the templet having been set to indicate 
this, and the brick lining is then laid as above described. If 
concrete is used and is not carried to the sides of the trench 
(see Plate VI, Fig. 9) a form of plank is used, inside which 
the concrete is rammed, and the plank removed when this is 
set. If the trench is sheathed and the concrete is built 
against the sheathing this cannot be pulled, but must be left 
in or cut off above the concrete. If stone masonry is used 
for invert-backing it is better to lay the course of stone next 
to the brick lining with radial beds. 

If concrete is used for the entire sewer special forms must 
be made for each size of sewer, at least two sets being in use 
by each gang. The form for the invert may be made similar 
to an arch-centre, except that the lagging must make tight 
joints (its edges being bevelled to permit of this) and only the 
two or three on the bottom be fastened to the templets. 
This form is fixed in position, concrete is placed in the 
bottom, between the lagging and the earth, and rammed; one 
or two strips of lagging are then slipped into position on each 
side and concrete placed and rammed behind these; more 
strips are added and concrete rammed behind them, and so 
on until the concrete is brought to the springing-line of the 


PRACTICAL SEWER CONSTRUCTION. 305 

arch. The forms should not be removed until the concrete 
is set. There is much danger that in this invert construction 
dirt and stones will get into the concrete, to its detriment, 
and great care must be taken to avoid this. The forms must 
be strongly braced down from the bank, to resist their ten¬ 
dency to rise when the concrete is rammed. The concrete 
should be just wet enough to permit water to be brought to 
the surface by light ramming. No heavy rammers should be 
used. 

For making a concrete arch, if there is no brick lining, 
a centre is used with close lagging, or an open-lagged centre 
may be covered with sheet metal, as on the Wachusett 



Fig. 26.—Form for Concrete Arch. 


Aqueduct mentioned above. The outside form may be con¬ 
structed as shown in Fig. 26, the forms being placed 3 to 5 
feet apart, the lagging being loose and put in one strip at a 
time. 

Concrete sewers have been built in a “ travelling mould ” 
(Ransome method), by use of which the entire sewer is con¬ 
structed continuously, foot by foot. A core in the shape of a 
ribbon which can be readily withdrawn after use (Chenoweth 
system) has been used for small concrete sewers, to which the 
use of the ordinary centre and form is not adapted. 





















3°6 


SE WEE A GE. 


A 42-inch sewer was built in Coldwater, Mich., in 1901, 
with a monolithic concrete invert, the arch being of concrete 
voussoir blocks 5J inches by 24 inches on the intrados, which 
construction was found to be cheaper than brick, and satis¬ 
factory otherwise. 

Art. 75 . Building Manholes and Other 

Appurtenances. 

These can most conveniently be, and usually are, built of 
brick. The foundation is sometimes of brick, but concrete 
is better in most cases. A stone slab set on concrete makes 
a good bottom for catch-basins. 

The channel through a pipe-sewer manhole is sometimes 
built of brick, but a split pipe is better. If brick be used, 
the inside of the channel should be plastered with a coat of 
neat Portland cement. If any branch channel in a manhole 
is not to be used at once it should be temporarily closed to 
prevent deposits forming in it. The bench may be built up 
of brick plastered on top with cement, or of concrete. Or 
the whole manhole bottom may be of concrete, a wooden core 
being slipped into the opposite pipes and spanning the man¬ 
hole to give the shape to the channel. 

In leaving the manhole-opening in a brick sewer the end 
brick in every alternate course of the outside ring may be 
laid radially, thus presenting toothing protruding at right 
angles to the sewer-barrel. In this steps with horizontal 
treads can be built of brick trimmed to the necessary shape, 
from which the manhole can be carried up without danger of 
its sliding off the sewer. 

To insure having the manhole of the proper size and shape 
a board templet may be used, being laid, in pipe-sewer man¬ 
holes, upon the concrete foundation when this has set, and 
the brick started by it and carried vertically to the proper 


PRACTICAL SEWER CONSTRUCTION. 307 

height. Another templet 24 inches diameter is fastened at 
the level of the top of the brick-work, its centre vertically 
above that of the bottom templet. Cords are strung from 
the edge of the top templet to the top of the vertical part of 
the brick wall, spaced about 2 feet apart around its circum¬ 
ference, and the brick laid to these. An experienced man¬ 
hole mason, however, can build almost as symmetrical a 
manhole by eye only, and more quickly than if strings are 
used. 

When the wall is about 2 or 3 feet high the benches and 
channels of the bottom may be constructed. It is well to lay 
plank in the bottom over the channels temporarily, to keep 
mortar and dirt out of them and out of the sewer during con¬ 
struction, as well as to hold the brick and mortar being used. 
The first step should be placed about 18 inches or 2 feet above 
the bench. When the wall is about 4 feet high four piles of 
brick, each 8 inches square and about 3 feet high, may be 
made on the bottom of the manhole and a platform of short 
loose plank be placed on these, entirely filling the manhole. 
This holds the mason, brick, and mortar until another 3 feet 
are built, when a second platform is similarly placed 3 feet 
higher. These are of course removed when the brick-work is 
completed. 

The brick in a manhole may be laid as all headers, all 
stretchers, all on end with their edges exposed, or a combina¬ 
tion of any two or all of these. Bats may be used in large or 
small proportion or not at all. A strong manhole can be 
built by using three courses of stretchers to one of headers, 
all whole brick, until a diameter of about 3 feet is reached, 
and from there to the top using three courses of squared bats 
to one of headers. The outside of the manhole should be 
plastered as the wall is built, since it may be impossible to 
reach it afterward. The head should be set as soon as the 
brick-work is completed, and the opening back-filled. 


3°8 


S£ WEE A GE. 


If the manhole is shallow, or for any other reason the 
diameter is to be rapidly reduced towards the top, this is 
ordinarily done by making each ring of brick a little smaller 
than the one below, the diameter of the manhole being 
reduced by i to 4 inches with each ring. Or it may be 
arched (Plate IX, Fig. 2), when the back-filling around it 
should be thoroughly tamped to assist in taking the thrust. 

4 

In the case of flush-tanks particularly a flat iron ring is some¬ 
times built in the outside of the brick-work at the bottom of 
the arch as a precaution. 

Flush-tanks are built in a manner similar to the above. 
These, except at the very top, and catch-basin inlets, are 
usually larger in diameter than manholes, and are built 
throughout of whole brick. Extra care should be taken to 
have all joints filled with cement and tight, and the work well 
bonded. After the cement in flush-tanks and catch-basins 
has fully set they should be given on the inside two or three 
washes of neat-cement grout, laid on with a whitewash or 
similar brush, care being taken to cover the entire sur¬ 
face with each coat, which should be allowed to dry before 
the next is applied. This will seldom fail to give a tight 
wall. 

No water should be turned into the trench for flushing or 
other purposes before the cement in these appurtenances, as 
well as in the sewer, has set. 

If masonry in either sewers or their appurtenances is laid 
in freezing weather special measures and precautions should 
be taken. The sand, stone, brick, and water should all be 
heated before being used, and special care taken to see that 
no ice or frozen dirt is in the mortar, on the stone or brick, 
around the sub-drain, under the pipe, or under or behind the 
brick or concrete sewer-invert. To insure the last it is well 
to take out the last foot or two of trench just before the sewer 
is to be laid in it. If any frozen earth is found under the 


PRACTICAL SEWER CONSTRUCTION. 309 

sewer grade it should be removed and replaced by sand or 
gravel thoroughly rammed. 

The water for mortar can be conveniently heated by 
injecting into it steam (as the exhaust from a pump- or exca¬ 
vator-engine), it being kept in several hogsheads or oil- 
barrels. The brick and stone can be heated by piling them 
as in brick-kilns and burning a wood fire under them; and the 
sand by being piled over these, or in large iron pans such as 
are used for heating asphalt. 

Art. 76 . Foundations. 

Piles are ordinarily used for sewer-foundations in soft soil. 
They usually support a timber platform, but in some instances 
concrete is placed directly upon and around their heads. For 
driving them the ordinary pile-drivers are used, or they are 
sunk by the water-jet. If they are to support platform 
timbers they must be driven carefully to line and sawed off 
accurately to grade. It will sometimes be advisable to drive 
the piles before the excavation has proceeded very far, using 
piles considerably longer than actually required, as the jarring 
of the banks of the trench may thus be avoided, as well as the 
inconvenience of moving the driver through or over a trench 
full of braces. The objection to this plan, aside from the 
cost of the additional length of the piles, is that they interfere 
with the excavation. 

In moving an ordinary pile-driver through the trench it 
will be necessary to remove the braces ahead of it. But no 
brace should be removed until another has been inserted 
behind the driver-frame between the same rangers and as 
close to the first as possible. This trouble might be avoided 
in many cases by placing the pile-driver on a track, on a level 
with the ground, over the centre of the trench; or the track 
may be on the surface at one side of the trench. The driver 


3 io 


SEWERAGE . 


is then provided with movable hammer-guides, which can be 
lowered into the trench and raised with ease. The use of the 
steam-hammer pile-driver is often advantageous, and in sandy 
soils the water-jet can be used to advantage. Neither of 
these last is interfered with in its operation by the bracing. 

The dimensions and construction of the platform follow 
the rules for ordinary foundations. There is usually but one 
set of timbers under the planking, which is in most cases 
composed of one or two layers of 2-inch to 4-inch plank, as 
in Plate VI, Figs. 3, 5, and 6; although in some instances 
heavy timbers are used, as in Plate VII, Fig. 10. Any 
timber which is to be placed where it will not be continually 
wet should be creosoted. 

If a platform is used without piling, sills, longitudinal or 
cross, should be placed under the planking, although in the 
case of small sewers these may consist of lengths of 2-inch 
plank only. Platforms without piling or heavy sills are of 
little permanent service under large sewers, but during con¬ 
struction may serve to prevent local distortion of the masonry 
before the cement has set. One or two lines of plank placed 
lengthwise under a pipe sewer, however, are in many cases of 
permanent value, back-filling being thoroughly filled and 
rammed between the pipe and the plank. 

Among the best of our woods for foundations are the 
cedar, oak, elm, alder, and beech. All bark should be 
removed and the sap dried out from piling or sawed timber. 
The platform timbers should be fastened to the piles with 
iron drift-bolts or treenails. 

Art. 77 . Pumping and Draining. 

Next to quicksand, water is probably the worst enemy of 
the sewer-contractor and requires a large share of the atten¬ 
tion of the engineer. If there is but a small trickle or ooze 


PRACTICAL SEWER CONSTRUCTION . 311 

of water into the trench it may interfere but little with the 
excavating, and will collect at points in the bottomed trench 
whence it can be removed at intervals by a bucket. If the 
amount becomes somewhat greater it may still be handled 
without the use of sub-drains, that from where the pipe has 
been laid being shut off by the back-filling. 

The amount from the trench ahead of the sewer may need 
to be pumped, however. For removing small quantities of 
water from a trench probably nothing is better than a 
diaphragm-pump. Tin “boat-pumps” are often used, but 
will not handle so much water, are less economical of power, 
and are not so convenient as the diaphragm-pump; they can, 
however, be used in trenches more than 20 feet deep, where 
the diaphragm is hardly practicable. Under favorable condi¬ 
tions a diaphragm-pump can be made to raise 5000 or 6000 
gallons per hour. Diaphragm-pumps can be used in deep 
trenches by placing a second pump upon a platform half-way 
down the trench, which discharges the water into a tub, from 
which the first pump raises it to the surface. Or the upper 
pump may not be used, but a trough may carry the discharge 
from the lower one to an opening in the sewer at a point 
where the cement is so set as to be uninjured thereby, the 
water flowing through the sewer to its outlet. 

A sump-hole of ample size should be made in the bottom 
of the trench to receive the suction-pipe, which should be 
provided with a strainer at the bottom. If the material is 
sand or soft ground it is well to place a pail or keg in the 
sump to keep the end of the suction-pipe from being buried, 
the top of the pail being just below the level of the trench 
bottom. The pail should be watched and material kept from 
running over its edge. The excavation should usually be so 
carried on that the whole trench slopes toward the sump-hole, 
each laborer seeing that the water flows through his section 
to the next lower. 


312 


SE WEE A GE. 


Where a sub-drain is being laid the water is frequently 
permitted to flow from the trench under excavation to and 
through this. In many if not most soils this is bad policy, 
since it leads to a silting up of the drain by the large amount 
of material washed in from the trench. It is better in most 
cases to leave or make a dam at the upper end of the com¬ 
pleted trench, and place a sump-hole just ahead of this and 
below grade, from which the water is pumped. When a sec¬ 
tion of 20 or 30 feet has been excavated to grade another 
dam and sump-hole can be placed at the head of this section 
and the others removed, the sump-hole being filled with sand 
or gravel or other good material well rammed. 

Where a sub-drain is started from a sump-hole, or that 
lower down the line is found to be too small to carry the 
water coming to it, a pump must be placed at this point also 
to remove the water from the sub-drain which is to be laid 
beyond it. This water is frequently raised to the sewer only, 
the pump being placed in a manhole and discharging the water 
below a temporary dam in the sewer, which prevents its flow¬ 
ing up the sewer onto the work. 

Two or more hand-pumps are sometimes concentrated at 
one point when the amount of water is considerable. It 
would in many instances be cheaper to use a steam-pump at 
such a place. Piston, centrifugal, and wrecking pumps, 
pulsometers, and steam-siphons are the steam appliances in 
most common use on sewer construction. In all of these iron 
suction-pipes are used, from 4 to 8 or 10 inches in diameter. 
The piston-pump is the most economical, and adapted to 
widely and rapidly varying quantities of water, and if the 
water is fairly clean needs very little attention. It cannot, 
however, pump gritty water without rapid deterioration. The 
centrifugal pump can raise muddy or gritty water, chips, and 
even small stones, its first cost is less than that of a piston- 
pump, and it can be repaired more cheaply if damaged. It 


PRACTICAL SEWER CONSTRUCTION. 313 

requires a fairly constant and fixed quantity of water to keep 
it working, and is apt, especially when a little worn, to give 
trouble by losing its priming, when the rising of water in the 
trench before it can again be primed may give trouble. The 
wrecking-pump the author has found to be an excellent pump 
for sewerage-work. It will lift and discharge anything which 
can pass through its suction-pipe and is extremely simple in 
action. All these pumps must be firmly set over or near the 
trench and their position can be changed only with consider¬ 
able labor. It is better to set them directly over the sump 
and have a suction-pipe as short and with as few joints as 
possible. 

The pulsometer pumps muddy and gritty water, but is 
not economical of steam and, except in experienced hands, 
is apt to act in a provokingly contrary manner, particularly 
after some use. It has the great advantage, however, of 
portability, being suspended by a chain, which permits rapid 
changing of its position without cessation of pumping, the 
steam being conveyed to it through a rubber steam-hose. 
For pumping large quantities of water at the point where 
excavation is proceeding and where frequent change of location 
of pump and suction is necessary it is perhaps the best contri¬ 
vance on the market. The steam-siphon is likewise conve¬ 
niently portable, but is most extravagant of steam and is 
hardly practicable for raising large quantities of water. 

The pulsometer and siphon are particularly adapted to 
raising water from the point where the work is progressing 
with the least interference therewith. Piston, centrifugal, 
and wrecking pumps are best used at a distance from the work 
to lift water which has flowed to them through sub-drains or 
the sewer, although they are often used at the work when the 
same sump can be used for two or three days at a time. 

All suction-pipe on either steam- or hand-pumps should be 
provided with a strainer at the bottom, and the centrifugal 


3H 


SE WERA GE. 


requires a foot-valve, which it is also well to supply for the 
other steam-pumps. If a chip or other obstacle should hold 
this valve open and prevent priming the suction a shovelful 
of stable manure dropped into the suction-pipe will in many 
cases enable the valve to hold its priming. 

All parts of the machinery should be readily accessible, 
particularly any valves, and wrenches and screw-drivers, pack¬ 
ing, oil, waste, duplicate nuts, washers, etc., should be kept 
constantly at hand. A cessation of pumping for 15 minutes 
may permit the water to drive the workmen from the trench, 
to soften the banks and endanger the sheathing, ruin the 
green masonry, stop up sub-drains, or do other serious 
damage. A good, intelligent, careful stationary engineer is 
a necessity on such work. 

The water raised from the trench should not be discharged 
upon the ground near the sewer, unless the street has imper¬ 
vious pavement, as it might soak back into the trench and be 
pumped over and over again. It may be carried to the 
nearest watercourse or sewer-inlet or manhole along the 
gutters, in wooden troughs, or in sewer-pipe temporarily laid 
on the ground with joints tightly calked with oakum or clay. 

It usually pays to keep the water pumped down all night, 
even if there is no work to be damaged by its rising, as this 
would again fill the surrounding ground with water, which 
might not drain out for several hours after pumping began the 
next day. It may be well to whitewash one or two sheath¬ 
ing-plank down to the trench bottom each evening, which 
will give evidence next day if the engineer has not kept the 
water down. A shelter should be built in front of the boiler 
to protect the engineer from storms. 

While using a diaphragm-pump always have spare dia¬ 
phragms and an extra length of suction-hose on hand. 

Moving a pump and boiler often costs more indirectly in 
interference with the work than the immediate expense comes 


PRACTICAL SEWER CONSTRUCTION. 31 5 

to. In general every effort should be made to set the pump 
in such a place and manner that it need not soon be moved. 
Be sure to have the blocking under it solid, to prevent the 
suction-pipe joints from working loose or breaking. 

Art. 78. Handling Wet and Quicksand Trenches. 

If excavation is in good material and of comparatively 
uniform depth a sewer gang once organized should move along 
at a uniform rate of 300 or 400 feet a day for small pipe 
sewers, 25 to 200 feet for brick ones, and with little but 
routine work for the foreman. If genuine quicksand is en¬ 
countered, however, every foot of progress must be fought 
for with unflagging energy, pluck, and intelligence. In 
ordinary wet trenches the difficulty, while not usually so 
great, is sometimes considerable. In both an intelligent 
adapting of the work to every new exigency is necessary. 

Water is met with as springs in the trench or as a general 
exuding from all the ground. The former can easily be 
managed by catching the water at its point of exit and pump¬ 
ing it away. If it enters from the bottom of the trench it can 
sometimes be caught in a trough and led back and discharged 
into either the completed sewer or into a tub in which the 
suction-pipe of a pump is placed. It is absolutely useless to 
attempt to stop the water from coming out of the ground; 
the endeavor must be to handle it after it gets out. In the 
case of a spring in a brick-sewer trench a method often advan¬ 
tageous is to build into the brick-work opposite the spring a 
small pipe, 2 to 4 inches diameter, through which the water 
can enter the sewer, and to conduct it back from there to the 
finished sewer in a trough. This pipe can be plugged after 
the masonry is thoroughly set, but might better be left open 
to drain the ground if in a storm-sewer, or if in a combined 
sewer and well above the line of flow of house-sewage. This 


3ie> 


SEWERAGE. 


pipe can, in many cases, be so driven into the bank at the 
spring that the water will flow through it and the trough be 
set before the brick-work is begun at that point, the trench 
being thus left dry. 

If the water does not enter as a spring and consequently 
cannot be caught in this way, but if the ground is a gravel 
or is not readily softened by the water, an outer ring of brick 
may be built with quick-setting cement, and plenty of it in 
beds as well as joints, an occasional brick being left out to 
permit the water to enter the sewer-invert, over which it can 
flow to a sump-hole ahead or through the sewer below. If 
openings are not thus left in the brick-work the water will 
force its way through the joints. Plank should be placed over 
the brick-work as fast as it is laid for the masons to stand 
upon. This outer ring when set may be found uneven of 
surface, but the joints will probably be tight. The openings 
may then be closed by inserting a brick and calking the joints 
with cloth, oakum and cement, wooden wedges, tea-lead, 
etc., or a pipe may be inserted and the water allowed to enter 
it as described above. The outer ring being thus made 
water-tight, the inner ones can be built as usual, any depression 
in the outer ring being well filled with mortar. In this and 
in all brick-, stone-, and particularly concrete-work which water 
flows over while green the surface can be protected from wash 
by spreading rather heavy, strong brown wrapping-paper over 
it. Cheap wood-pulp paper is of little use. The paper when 
wet will cling to the masonry, remaining intact for days and 
even weeks. 

Another plan is to dig a sump-hole ij to 3 feet deep in 
the centre of the section of invert under construction, and 
keep the water lowered in this by a pump until the brick-work 
is completed and set everywhere except over the sump. If 
the ground is very porous the water will all flow to the sump 
and leave the trench dry for several feet in each direction. 


PRACTICAL SEWER CONSTRUCTION. 317 

When the surrounding masonry has set the suction-pipe is 
removed from the sump-hole, and this is filled with sand, 
gravel, or concrete, thoroughly rammed. The remaining 
brick-work is then laid, with or without a pipe through it, as 
described above. 

A better plan is to use sub-drain pipe, discharging into a 
sump, which is to be pumped if there is no outlet for it or if 
the drain below is too small to carry all the water. A disad¬ 
vantage in this connection of building either brick or pipe 
sewers down instead of up grade is that the water cannot be 
run away through the sewer or sub-drain, whether it be 
pumped or not, and although it drains away from the work it 
is only to soak into the ground ahead and make that all the 
wetter, besides the fact that it is accumulated where the 
excavation is in progress. Not only this, but the ditch acts 
as a drain to conduct down to the work water from all the 
territory above which has been passed through, the use of a 
sub-drain adding greatly to this amount. If the trench be 
dug up hill it will while advancing tend to drain out the 
ground ahead and a trench may be found dry which would be 
wet if approached from above. In some instances where a 
trench has been extended up to ground which seemed hope¬ 
lessly wet, and the trench thoroughly braced and left open for 
a week or two, the excavation was then resumed without diffi¬ 
culty, the ground being found comparatively dry. 

This fact, that wet ground will in many cases drain out if 
an outlet be provided, may be taken advantage of in several 
ways. For instance, if beneath the wet porous soil, but 
above the sewer grade, is a stratum of clay the trench may 
be carried down to this, braced, and allowed to drain out, 
when the clay can be readily cut out dry instead of as a thick, 
sticky paste which mires the feet and will not leave the 
shovel. Quicksand can sometimes be dried out if the water 
be given an outlet and sufficient time allowed. It will then be 


3>8 SEW ERA GE. 

almost as hard as rock, but much easier to handle than in its 
quick state. 

If sewer construction is in the shape of an extension from 
a line already in use into which the water must not be run, or 
if it is carried on in sections which have no outlet, a pumping- 
station can take the place of an outlet, or a ditch can some¬ 
times be carried to a watercourse lying below the sewer. The 
latter is always the better plan if not too expensive, as there 
is then no danger from broken or disordered pumps. But the 
ditch must be above the reach of any possible flood in the 
stream into which it discharges. 

A plan used with success on the Metropolitan Sewerage 
System (Boston) and elsewhere is to drive 2- or 2^-inch pipes 
by water-jet on one or both sides of the trench, io to 15 feet 
apart and to a point 2 or 3 feet below the bottom of the 
sewer, and, by connecting a number of them to a 6-inch 
suction-main and pumping on them for a few days, lower the 
ground-water before the excavation reaches this point, and 
keep it lowered until the work here is completed. If the 
trench is less than about 20 feet deep the pipes may be driven 
outside the trench, but if more it will probably be necessary 
to put them and the pump inside the sheathing at a distance 
of not more than 20 feet from the bottom, although they may 
be in the way there. The sinking of such tubes in Newton, 
Mass., cost from 8 to 50 cents per foot. 

In laying pipe sewers in wet trenches much of the above 
is not applicable. The best method for such work is the use 
of sub-drains. When the ground is not excessively wet the 
trench is then dry for the laying of the sewer-pipe. But 
where there is a large flow of underground water it may be 
impossible for it to reach the sub-drain, through the overlying 
gravel or stone, as rapidly as it enters the trench. Frequent 
sumps must then be provided, with a pump at each, there 
being always one only a few feet ahead of the sewer. If 


PRACTICAL SLIVER CONSTRUCTION. 


319 



water still flows over the trench bottom to the sump it may 
be necessary to lay the sewer in concrete. In fact this is 
always desirable, though expensive, in wet trenches or where 
sub-drains are used. In using concrete it should be placed 
and rammed in the trench and 
the pipe bedded in it before it 
sets. The concrete may be 
brought up only a short distance 
above the invert of the pipe, 
being sloped down toward the 
sheathing and forming a gutter 
on each side in which the water 
may run to the nearest manhole 
or sump. If this flow is consid¬ 
erable plank or boards or heavy 
paper may be laid on the con¬ 
crete to protect it from wash. 

The rest of the sewer-joint may 
be made in the ordinary way. It 
is better, however, to also carry the concrete entirely over the 
sewer at the joints after a stretch between manholes is com¬ 
pleted and the side gutters are no longer needed. 

Water should never be allowed to stand in bell-holes after 
a pipe is cemented. If liable to, the bell-hole should be filled 
with cement or concrete, or at least with sand or gravel well 
tamped. No water should be allowed to run through a sewer 
until the cement is fully set. Particular attention should be 
paid to branches and slants in wet trenches to see that they 
are tightly sealed. It is an excellent plan to build a dam at 
each end of a stretch of sewer in a wet trench, after the sewer 
is completed and cement set, and before back-filling above 
the pipe, and allow the water to stand upon it Leaks thus 
discovered are then readily accessible for repairs. 

In moderately wet ground it is often advisable to place 


Fig. 27.- 


-Sewer-pipe Laid in 
Concrete. 











320 


SE WEE A GE. 


dams across the trench at intervals of 15 to 30 feet, that there 
may not be so great a stream continually flowing by the men 
while working. The head of the trench being kept on an 
incline, water collects above each dam until there are no dry 
places left in the sections in which to dig, when the dams are 
opened in succession, beginning with the lowest, and the water 
flows to the sump, from which it is pumped. The dams are 
then closed and digging resumed immediately above each, the 
laborers moving up the slope as the water rises above each 
dam. 

The combination of water with a particular kind of sand 
produces what is called quicksand. Any object resting upon 
this sinks slowly into it until it has displaced its own weight 
of sand. But a pick can hardly be driven into quicksand 
which has not been disturbed. The sand is very fine and is 
easily stirred up and carried by running water, but will 
quickly settle into a tough, compact mass which, if allowed 
to dry out, will become almost as hard as soft sandstone. 
Quicksand is semi-fluid and will run under sheathing unless it 
be driven to a considerable distance below the bottom of the 
trench. If the influx is not cut off by deep sheathing, by the 
time the excavation is 2 or 3 feet into quicksand a point is 
reached beyond which no headway can be made, the bottom 
remaining at the same level however much be taken out of it. 
After a time the cavities behind the sheathing, caused by the 
flowing of the quicksand from there into the trench, permit 
the ground-surface to settle or to drop entirely, and the 
sheathing, relieved of outside pressure and friction, is apt to 
completely collapse. If there is any possibility that such a 
cavity is forming all braces should be nailed to the rangers 
and tied together by cross-bracing, and outside rangers braced 
against the sheathing from the curb or other points well back 
of the trench. If there is more than one course of sheathing 
the plank in the upper ones should be nailed to the rangers. 


PRACTICAL STIVER CONSTRUCTION. 


321 


If the ground-surface should fall into the cavity thus made 
sod, straw, brush, etc., should be thrown against the sheath¬ 
ing, which will stop the quicksand from flowing into the 
trench. The entire cavity should then be filled with earth, 
ashes, or some good filling material. It is in most instances 
well, if the condition is such as is shown in Fig. 28, to remove 



a plank or two here and there from the upper course of 
sheathing and throw into the cavity sods or straw, and then, 
after bracing the sheathing as above described, to break down 
the top soil and fill the cavity with good earth. Fig. 28 is 
no exaggeration of conditions sometimes occurring in quick¬ 
sand. A preventative, which is usually effective, is to keep 
several men continually driving the sheathing with light 
mauls, or better still keep steam-hammer pile-drivers at work, 
so that the bottom of the sheathing is continually maintained 
a foot or two below the bottom of the trench. This is a pre¬ 
caution which should never be neglected. 

One effect of the formation of the cavities described is 
that the top earth tends more than ever to fall towards the 































322 


SE WEE A GE. 


trench, and consequently the strain on rangers and braces 
becomes severe. It is better to multiply the number of 
rangers than that of the braces to each ranger, as the trench 
is then less obstructed for lowering materials. 

Quicksand has usually only a little water flowing through 
it, but that little should be handled by pump if possible and 
not allowed to run into the sewer or sub-drain, the result of 
which would be the- rapid choking of the drain, or of the 
sewer if small, by quicksand. Quicksand should not be 
thrown directly back upon the finished sewer, as its angle of 
stability is exceedingly small, and it is apt to run forward to 
the upper end of the sewer, either requiring to be handled over 
again or flowing into the mouth of the pipe. If thrown upon 
the bank and dried out, however, it becomes very hard and 
expensive to shovel back. It is probably better to back-fill 
with it immediately at some distance from the sewer under 
construction, carrying it there by excavating-machinery or in 
wheelbarrows, or to let it partly dry upon the bank before 
throwing it back. It is well to have a few short plank nailed 
together to form platforms which can be placed in the trench 
bottom for the men to stand upon, as otherwise they will lose 
much time digging themselves and each other out. The 
length of open trench should be kept short and the men 
worked as close together as practicable, and sub-drain with its 
gravel and platform put in and sewer laid as rapidly as possi¬ 
ble. Even then the danger is not over, as the structure is 
liable to be raised out of place by inflowing quicksand. A 
pipe sewer which had been laid in quicksand and covered with 
the same material as back-filling has been known to rise more 
than 3 feet overnight, practically floating to the surface of 
the quicksand. To prevent this a plank may be laid over the 
sewer and braced down from the sheathing and the pipe thus 
held in place. 

In the case of a brick sewer the platform should generally 


PRACTICAL SEWER CONSTRUCTION. 323 

be set upon piles (which can best be driven by the water-jet) 
and immediately loaded with brick or stone which is to be 
used in the construction. It is advisable in most cases of 
large sewers built in quicksand to place close sheathing across 
the trench, 15 to 30 feet ahead of the completed sewer, mak¬ 
ing a coffer-dam, inside of which the next section of sewer 
is built. Meantime other cross-sheathing, 15 to 30 feet still 
further ahead of the last, is being driven, together with 
the side sheathing, and the coffer-dam thus formed excavated. 
When this is down to grade and the foundation in, the cross¬ 
sheathing just ahead of the completed sewer is removed and 
the sewer continued into the next section of trench. In each 
of these coffer-dams, usually in one corner, is a sump from 
which the water is kept pumped. A pail or barrel should be 
used in every sump in quicksand and the sand kept dug away 
from around it, as it is very apt to reach and stop the suction- 
pipe, from which it is difficult to remove it. Gravel or fine 
broken stone may be placed around the barrel and carried a 
few inches above it to prevent the sand reaching it. 

Laying pipe sewers in quicksand may be even more diffi¬ 
cult than building brick ones. If a platform foundation is 
used there is not sufficient weight in the pipe to hold it down 
and it must be strongly built and braced down from the 
sheathing. The following plan has worked well: A sill of 
4X6 timber is laid near each side of the trench, which has 
been brought as near as possible to grade, and a short piece 
of plank is stood upon it near one end. Two or more men 
then stand upon the sill near this end and work it down to the 
necessary depth, when the upright is nailed to a brace or 
ranger and the sill at this point thus held down to place. The 
other end is then worked to place and similarly braced and 
the other sill treated likewise. By this time the sand is prob¬ 
ably several inches deep over both sills. Cross-planking for 
the platform having been sawed to length—the closer they fit 


324 


SE WEE A GE . 


between the sheathing the better—one at a time a place is 
cleaned for them and they are nailed to the sills with close 
joints. Good material is then placed on this platform and the 
pipe laid thereon and the same material immediately back¬ 
filled around and above it. When the pipe has been laid to 
the end of the platform it should be tightly plugged, if the 
next platform is not ready to continue laying (as it probably 
will not be), to keep out the quicksand, which may rise above 
the pipe-invert before the laying is continued. 

Another plan for laying sewer-pipe, and an excellent 
one for sub-drains, in quicksand is as follows: Two planks, 
each about 6 feet long, are stood upon edge a sufficient dis¬ 
tance apart to permit laying between them the sewer-pipe, or 
drain-pipe and required broken stone, and a strip of wood is 
nailed across their tops at each end. The other edges are 
then turned up and similarly treated, a bottomless trough 
being thus formed. A loose bottom is provided to fit it, 
usually in two or three pieces. The bottomless trough is 
then placed in the trench with the plank on edge and worked 
down into the quicksand until to the necessary depth and in 
the correct line, and is braced down from the sheathing. The 
sand is then shovelled out of this and the bottom planks put 
in, one at a time, the men standing on the trough bottom 
until all the planks are in and secured, which is effected by 
placing a cleat across the bottom at each end and fastening it 
to the sides of the trough. The sewer, or sub-drain and 
broken stone, are laid in this and good material is packed 
around and over the sewer. This method is also adapted to 
dry running sand, where the trough can generally be used 
without a bottom. 

Another method sometimes employed is to excavate the 
quicksand in short sections somewhat below the pipe-level 
and refill it with cinders, or spread burlap over the bottom 
and cover it with gravel, on which the sub-drain or sewer is laid D 




PRACTICAL SEWER CONSTRUCTION. 325 

Still another plan is to drive tubes a few feet apart through¬ 
out the entire trench, a few at a time, their bottoms being all 
about a foot or two below the pipe grade, and inject cement 
and water under pressure, the cement filling the interstices of 
the surrounding sand and forming an artificial stone, which 
prevents the quicksand from rising. The pipes are then 
removed and the trench excavated. This process is patented 
and expensive. 

In laying sub-drains through wet soils, particularly wet 
sand, a great deal of annoyance and expense will almost 
surely be incurred if some plan is not carried out for keeping 
the pipe free from deposits, which will form from the dirty 
water flowing into the end of the pipe. Probably the best 
plan is to keep a rope drawn through at least 600 feet of the 
pipe, the end being drawn forward through each length as it 
is laid. At intervals of from 10 minutes to half a day the 
rope should be pulled back and forth to stir up the deposit 
and keep it moving. It is well to knot up a light chain and at 
least once a day tie it firmly to the rope and draw this through 
the drain a few times. If the rope is neglected for too long a 
time it may become imbedded in the deposit and require six 
or eight men or even a team to draw it through the pipe. It 
should be amply strong for this. When a section between 
manholes is completed the rope should be left in until the 
next section is completed, as a part of the dirt flowing through 
the upper will probably settle in the lower section. The latter 
should be cleaned at least once every day. It may be well, 
if the deposits are considerable, to fasten to the rope in the 
lower section a strap to which two or three tapering tin cans 
are riveted (see Fig. 29). These are drawn a little way into 
the pipe, closed end first, and then drawn back and the dirt 
emptied from them. (If started through the pipe mouth first 
they would probably pile the dirt ahead of themselves into an 
immovable mass.) When not in use these should be kept out 


326 


SEWERAGE. 


of the pipe, as should also the knotted chain above mentioned, 
to permit the free passage of water. 

It is advisable to flush the drain with comparatively clean 
water as often as possible. This may be done by catching 
the ground-water by dams, as described above, and, when the 
drain has been laid up to a dam, bailing the water rapidly from 
this into the drain. Or a plank may be set across the trench 
bottom just ahead of the pipe, so as to catch any mud or 
stones which may be washed down but permit the water to 



Fig. 29.—Appliance for Cleaning Sub-drains. 

flow over, and the dam be broken, but kept under control, so 
that it can be closed if desired. 

It is well to always keep in the end of the pipe a pan with 
fine holes over the upper half of its bottom, these holes form¬ 
ing the only entrance for water to the pipe. Sticks and stones 
are thus kept out of the sewer, as well as the water most thick 
with mud. If the water is clear the perforated part of the 
pan can be placed at the bottom. These remarks refer par¬ 
ticularly to sub-drains, since water should not be permitted 
to rise above the sewer-invert. 

The entire system of sub-drains cannot be flushed too 
often during construction—by hose from the fire-hydrants, if 
possible. If a drain is stopped up in which there is no rope, 
cr the rope cannot be moved, a hole can sometimes be forced 
through the obstruction by a line of f-inch or i-inch iron 
pipe. If this is fastened by a special bushing or otherwise in 
the end of a hose and water forced through it, it can be driven 
through in almost every instance if the friction between the 
iron pipe and the deposited material does not become too 
great. If the section in which the stoppage occurs is not at 
the incompleted end this plan cannot be adopted; but an old 









PRACTICAL SEWER CONSTRUCTION. 327 

length of 2^-inch hose with no coupling on one end can be 
placed at the end of a line leading from a fire-hydrant to and 
down a manhole, and this end pushed into the drain; when 
the water is turned on the hose can be pushed forward as if it 
were a flexible rod, and the water from the hose will wash the 
obstruction loose and bring it back to the manhole, where it 
can be removed from the sub-drain well by hand, the water 
rising up and overflowing into the sewer. Sand, gravel, and 
even brick-bats have been washed out of drains by this 
hydraulic process. 

When laying a pipe sewer the manhole is not usually con¬ 
structed until the sewer has been laid on each side of it. In 
quicksand if the trench is opened through where the manhole 
is to be it will immediately fill up above the sewer. The pipe 
must therefore be plugged at the end. It is, for this and 
other reasons, often desirable in quicksand to build the man¬ 
hole before the sewer reaches it, openings for the sewer being 
left in the manhole-wall at the proper points. The excavation 
for the manhole must be made in a well-hole close-sheathed 
for at least a foot lower than the sewer-invert. It will be 
found difficult to get the bottom in with the ordinary 
methods, particularly if there is a sub-drain well to be put in. 
In such a case the following plan has been used with success: 
A 12- or 15-inch pipe with two T branches of the size of the 
sub-drain, temporarily plugged, is lowered into position to act 
as the sub-drain well, the bell being up and the branches 
being placed at the grade of the sub-drain, which connects into 
them. The manhole excavation having first been carried to 
the depth necessary for the foundation, this pipe may be 
lowered by resting upon it with the knees and digging the 
sand from the inside, care being taken to keep it vertical and 
in the proper position. When it has reached the required 
depth the sand is scooped out a little below its lower end and 
one or two bucketfuls of concrete placed there and rammed 


328 


SEWERAGE. 


(see Plate X, Fig. 9). It is well to place a board bottom 
inside the pipe on top of the concrete and to place brick on 
this to keep the concrete from being forced up, the brick 
being removed after the concrete sets. If necessary another 
12- or 15-inch pipe is placed upright in the hub of this one. 
A length or two of drain-pipe is fixed in each branch of the 
sub-drain well in a horizontal position and in the proper line 
to connect with the sub-drain when laid, and the manhole 
bottom is then dug out to the grade of the bottom of the 
foundation and concrete placed there, before the sand rises, in 
small areas of 8 or 10 feet at a time. This is done rapidly and 
the concrete loaded with brick, if necessary, to hold it down. 
The concrete is placed last where the channel comes and a 
split-pipe invert is at once forced down in it to the proper 
grade, and a straight-edged plank placed on edge in the invert 
bottom and braced down from the sheathing to hold it in 
position. The formation of the manhole bottom is then com¬ 
pleted and the walls built in the usual way, sewer-pipe being 
built into the manhole-walls where the sewers are to enter it, 
but loosely enough to permit of sliding the pipe out. The 
sewer already laid or to be laid is carried through this opening 
by a pipe cut to the necessary length, the sheathing having 
been cut away here to permit this. 

Another plan is to lay a plank foundation for the concrete, 
one plank at a time being put in place and fastened to the 
sheathing, thus forming of the whole a tight box, in which the 
manhole is built. Flush-tanks, inlets, and other appurte¬ 
nances can of course be built in the same way. 

Art. 79. River-crossings and Outlets. 

For convenience of inspection and as permitting easier 
maintenance it is best to carry a sewer across a stream on a 
bridge or trestle, keeping its invert at the hydraulic gradient; 


PRACTICAL SEWER CONSTRUCTION. 


329 


unless, of course, this is below the river-bed, when the sewer will 
occupy that position. Very often the use of bridge or trestle 
is impossible or prohibitively expensive, and then an inverted 
siphon is necessary. In either case the pipe will probably be 
of iron or wood, although a combination of these with masonry 
is sometimes used. In some instances it may be better to 
build the siphon in tunnel, when it should be lined with brick 
or concrete; or, as is usually better, two or more iron or wood 
siphon pipes may be laid in the tunnel, easy access to them 
being thus afforded. 

A bridge or trestle for supporting a sewer should seldom 
be built of wood, owing to the difficulty of providing for the 
sewage when necessary renewals are being made. It may in 
some instances be unsafe to support a sewer by an existing 



bridge, owing to the great increase of load thus brought upon 
it. (An 18-inch cast-iron pipe flowing full of sewage will 
weigh about 225 pounds per lineal foot.) The bridge has in 
some cases been relieved of this weight by constructing the 
pipe in the form of an arch, but this is not generally advis- 



































330 


SE WEE A GE. 


able. A simple design for a short span, as over a creek, is 

« 

shown in Fig. 30; or the pipe could be supported inside an 
iron or steel box girder of suitable size and strength. There 
is no danger of the sewage freezing unless the pipe is exposed 
for a stretch of many hundred feet. 

If the distance to be crossed is more than 200 or 300 feet 
the inverted siphon will in most cases be found advisable. 
Its construction under water will be similar to that of river- 
crossings laid to grade, except that in the latter the most 
advantageous depth cannot be chosen. 

The joints and pipe of subaqueous siphons and other 
sewers should be perfectly water-tight, as it will be necessary 
at times to empty them of sewage for inspection. They should, 
if of small pipe, be laid to as straight a line and grade as any 
part of the system. If they are sufficiently large to be entered 
this is not so important. They should never be laid on the 
bed of the river, but always beneath it. 

For a sewer up to 30 or 36 inches diameter cast-iron pipe 
with lead or hardwood joints may be used. The trench is 
excavated at least 18 to 24 inches wider than the pipe and 6 
to 12 inches below its grade. Inside this trench the pipe is 
placed and suspended to grade or blocked up at intervals. 
The joints are made and concrete is placed under the pipe at 
all points, completely filling the trench for a distance of 2 or 
3 feet above the pipe, or to the surface of the river-bed, it all 
being thoroughly rammed. If the concrete does not reach 
the bed of the river it is well to throw loose stone over and 
along each side of it. 

If the river is not very deep, or a time can be chosen when 
such is the case, it is in many instances practicable to confine 
it to half the width of the bed, at the point of crossing, by an 
earthen embankment or timber coffer-dam, or combination of 
both, carried, just up stream from the line of sewer, from 
above the water-line out to mid-channel, across the line of 



PRACTICAL STIVER CONSTRUCTION . 331 

sewer, and back again to the bank a few feet lower down. 
The enclosed space is then pumped out, the trench dug and 
sheathed, the pipe and concrete put in position and covered, 
and the dam removed and a similar one placed upon the oppo¬ 
site side of the river, which then flows over the pipe already 
laid. In many cases the best form of dam for sewer-crossings 
is made by permitting the close sheathing of the pipe-trench 
to serve also as a dam, extending above the water-surface and 
backed by earth embankment. A brief statement of the 
details of carrying out this plan, which must, however, be 
varied under different conditions, is given. 

The sewer having been laid up to the river-bank, a stout 
stake is driven into the river-bed about io feet from the end 
of this and in line with the down-stream side of the trench. 
If necessary another is driven a few feet lower down and a 
brace set from the foot of this to the top of the former. A 
frame of rangers and braces is built upon the bank, of dimen¬ 
sions proportioned for the proposed trench, and floated to 
place in line with the trench already dug, the inner end being 
fastened in position against the end of this trench and the 
outer being held by the stake just mentioned. Sheathing is 
then driven on both sides and the end of this frame (the end 
braces are flush with the ends of the rangers) as deep as is 
possible before excavating is begun, and earth banked against 
the outside of it. The water is then pumped out and the 
trench excavated, the sheathing being kept driven as low as 
possible, additional rangers and braces being added, and the 
excavated material thrown just outside of it. When this 
trench is at grade the pipe is laid, concrete put in, and trench 
back-filled ahead to cross-sheathing which has been set just 
back of the end of the pipe. Another frame has meantime 
been started just ahead, sheathing driven, and outer embank¬ 
ment made. The cross-sheathing between the new and the 
completed trench is drawn and the excavation continued. 


332 


SEWERAGE. 


Cross-sheathing is set at frequent intervals and the trench filled 
up to it to reduce the length of open trench which must be 
kept free of water. It is advisable not to cut off the sheath¬ 
ing and remove the embankment at any point until the con¬ 
struction is completed to mid-stream. It will usually be 
necessary to keep a pump going constantly during construc¬ 
tion. If the stream is subject to freshets it may be well to 
set the pump upon a flat-boat anchored against the up-stream 
sheathing. The boiler may be kept upon this boat or upon 
the bank, the steam-pipe in the latter case being carried along 
the sheathing. 

If the bed of the river is gravelly considerable trouble may 
be experienced from water leaking into the trench, the enter¬ 
ing water having perhaps passed into the ground many feet 
from the sheathing. The embankment may in such a case 
be carried as far as possible from the sheathing on every side, 
or a thin layer of fine sand, sandy loam, or loamy clay may be 
spread over the bottom for 50 or 75 feet above and below the 
trench. Also manure, brewery-meal, etc., has been used to 
stop up the pores of the gravel. Heavy, closely woven 
canvas is excellent for use in such a case, in large squares or 
strips tightly sewed together, one end being fastened above 
water against the outside of the sheathing, the other anchored 
by stones or other weights beyond the part of the bed which 
is giving trouble. 

An excellent material for the embankments is a puddle of 
clay, sand, and gravel. Clay alone is almost useless. Fine 
and coarse sand mixed, with or without gravel, is better than 
clay alone. All sticks, roots, and large stones should be 
removed from this puddle, and anything which, reaching 
through the embankment, may offer a course for the water. 
If puddling material is scarce a double row of sheet-piling may 
be carried around the work, the two rows being from 2 to 5 
feet apart, braced together only at the top, and the space 


PRACTICAL SEWER CONSTRUCTION. 333 

between them filled with puddle well worked and rammed. 
Experience in this class of work is almost essential to its 
proper prosecution, and written directions can give only the 
barest outlines for meeting but a few of the difficulties which 
may be encountered. Pluck, foresight, a fertility in expedi¬ 
ents, and common sense are prime requisites for this work. 
The water must never for an instant be allowed to get the 
upper hand. If nothing else is at hand the very clothes off 
one’s back should be taken to stop a leak temporarily, should 



one unexpectedly develop in an embankment. Never permit 
a brace, stick, or any object to extend through an embank¬ 
ment or puddle-trench or -wall. If a trench surrounded by 
water shows signs of collapsing from outside pressure and no 
material for additional rangers and braces is at hand the 
trench can sometimes be saved by allowing water to fill it, and 
then, when the material has been obtained, the water can be 
pumped down and bracing put in as it lowers. But this is a 
somewhat desperate remedy. 

An outlet for the Massachusetts Metropolitan Sewerage 
System at Deer Island, in 5 to 10 feet of water, was built in 
open trench, with double sheathing and puddle, as in Fig. 31. 
The sewer was 6 feet 3^ inches inside diameter and the trench 
10 feet wide on the bottom, concrete being carried from about 
1 foot beneath the sewer to an average of 4 feet above it. 
“ The cost of the trench, including coffer-dam, sheeting left 



























334 


SE WEE A GE. 


in place, and back-filling, was $44 per lineal foot.” (Engineer¬ 
ing News, vol. XXXI, page 121 .) The material through 
which the trench was carried was sand and gravel. The work 
was done by day labor. 

If the trench is in rock or a tight coffer-dam cannot be 
made except at great expense it may be cheaper and better 
to resort to divers. When not in rock, however, the exca¬ 
vation of the trench should be done by a dredge or similar 
appliance if possible, as divers’ labor is very expensive. 

The end of an outlet which discharges at some distance 
from the shore of a stream or other body of water should be 
so located and designed that currents, tides, or storms cannot 
wash it full of sand or mud, that it cannot settle down into 
the bottom, that it cannot be undermined by tides or cur¬ 
rents, and that the sewage discharged will not settle in front 
of it and block the outlet. This may be accomplished by 
laying the sewer in a trench as described above, and at the 
very end placing a right-angled bend pointing upward and 
extending 1 to 3 feet above the bottom, this upright pipe 
being surrounded with a cone-shaped mass of concrete. Or 
the end of the sewer may be continued straight, but raised 
gradually until the outlet is 2 or 3 feet above the bottom, it 
being supported between two rows of piles back to where it 
has 2 or 3 feet of covering. 

It is not so necessary that an outlet pipe be straight in 
line and grade provided the grade continually falls at a suffi¬ 
cient rate. The use of flexible-jointed iron pipe, such as is 
frequently employed for water-pipes at river-crossings, may 
often be used for sewer-outlets. They should be properly 
protected by concrete, riprap covering, or piling. For 
furnishing and laying 2200 feet of 24-inch iron pipe with 
Ward flexible joints in a bottom consisting of sand, gravel, 
loose and solid rock, in a trench having an average depth of 
4 feet, the depth of water at high tide being 1to 30 feet, 


PRACTICAL SEWER CONSTRUCTION. 335 

from $16.85 P er foot to almost double this amount was bid in 
1898. In ordinary river-work the cost should be much less. 

Whenever subaqueous work of any considerable extent is 
being done it will be well to have a diver’s outfit on hand, as 
its immediate use may sometimes effect a saving of the work 
from serious damage. 

Art. 80 . Crossing Railroads and Canals. 

Railroads should be crossed with particular care, both that 
no accident may occur to either the workmen or to passing 
trains, and because of the difficulty of afterward repairing 
breaks or defects at such points. This applies also to sewers 
constructed in or close to the foot of railroad embankments. 

It is not advisable to tunnel under a railroad unless the 
sewer runs quite deep and the material is stable. A settling 
of the ground above the tunnel might prove disastrous to 
trains, and this settling is extremely probable, owing to the 
jarring of passing trains. If there is a culvert under the road 
through which the sewer can be passed it will often be well 
to take advantage of this, if only a slight detour be necessary 
in order to do so. 

If the sewer is to pass under the railroad in open cut each 
rail should be first supported by bridge timbers, beams, or 
iron rails placed under the ties lengthwise of the track and 
extending 10 to 20 feet beyond each side of the proposed 
trench. For a trench 4 to 6 feet wide a 12 X 12 bridge 
timber 25 or 30 feet long may be used. A heavy steel rail 
may be used under the same conditions, but is not generally 
so stiff. Each beam or rail is placed in a trench dug under 
the ends of the railroad-ties, just sufficiently deep and wide 
to enable it to be placed under the track-rail. Hardwood 
plank are then driven between this and the ground and 
wedges driven between each tie and the beam. The trench 


336 


SE WEE A GE. 


is then excavated, horizontal sheathing being used. The 
earth excavated cannot be thrown upon the surface unless the 
track is temporarily out of use. It may be handled by a 
cable-way excavator which swings sufficiently high to clear all 
trains. The buckets for this it will be well to have large— 
those holding a cubic yard will do—that the number of trips 
may be lessened. The back-filling can be returned in the 
same way and should be most thoroughly tamped. 

Another method of handling the earth, particularly ap¬ 
plicable where there are but two or three tracks, is to throw 
the excavated material beyond the outside track by one or 
two handlings, a space for this having been left clear of earth 
by previous management. If the trench is shallow and as 
short a len gth as practicable opened at a time it may even 
be possible to throw the excavated earth directly onto the 
completed sewer, but if this is done only a very few men can 
be worked at this point. 

After the completion of the work with thoroughly tamped 
back-filling the trench should be wet down every two or three 
days for several weeks, the bridge timbers or rails being left 
under the ties meantime. Just before each wetting earth 
should be placed and tamped on the filled trench to 2 or 3 
inches above the ties. When the trench shows no settlement 
after a wetting down the supporting timbers or rails may be 
removed. 

For small sewers it will be well to use iron pipe with lead 
joints for railroad-crossings, and for large sewers the arch and 
side walls should be reinforced (see Plate VI, Fig. 8). In 
general it is better to place no manhole or other appurtenance 
between or within several feet of any tracks. 

A trench in or near a railroad embankment is subject to 
the jarring of the trains and needs to be carefully sheathed. 
This is sometimes difficult if the trench be wholly or partly 
upon the slope of the embankment, since there is nothing 


PRACTICAL SEWER CONSTRUCTION. 


337 





Fig. 32.—Sheathing on Steep 
Slopes. 


opposite the upper ranger on the up-hill side against which 
to brace it. It will not usually be practicable to place a slop¬ 
ing brace from this to a lower ranger on the opposite side. 
A better plan would be to brace the sheathing against posts 
driven at intervals a little distance from the lower side of the 
trench and throw all the excavated material against this side. 
The sheathing on the lower 
side at least should be left in 
and protruding a short distance 
above the ground after the work 
is completed, to prevent the 
back-filling, which should all 
be thoroughly hand-rammed, 
from being washed down the 
bank by rain. 

It is not impossible to con¬ 
struct a sewer under a canal, 
raceway, or other body of water retained by embankments 
without drawing off the water or interfering with its service, 
but it is much easier and safer to do this work when, if ever, 
the water is out. The construction of a system can generally 
be so managed that all canal-crossings may be made in winter 
while the water is out, even if no other part of the system is 
constructed at that time. A raceway can in many cases be car¬ 
ried over the excavation temporarily by a flume extending for 
some distance in each direction from it. Care must be taken 
to prevent the water following the outside of this, for which 
purpose close sheet-piling may be used to advantage, being 
driven across the raceway at each end of the flume and 
making a tight joint with it. 

A sewer under or near a canal should be of iron pipe, 
unless too large, when concrete may be used, made very 
strong and extra thick—say 1 part Portland cement, 2 parts 
sand, 3 parts broken stone, with a 50-per-cent increase in 












338 


SEWERAGE . 



thickness over ordinary localities. If iron pipe be used cast- 
iron flanges made in halves should be bolted on the pipe at 
intervals, a thin lead strip being placed between the pipe and 
the flange casting to make a water-tight joint, or lead being 
calked into bells on the flange, as in the case of a sleeve-joint. 
Two or three of these flanges should be placed in each em¬ 
bankment and others io or 15 feet apart through the canal. 

All space under, around, and above the pipe 
should be thoroughly filled with puddled 
clay, gravel, and sand carefully rammed. If 
clay cannot be had loam may be used, free 
from roots or ** muck.” A good proportion 

Fig 33 —Flange ^ or these materials is I part of clay, parts 
for Pipe in Em- of sand, and 4 parts of gravel, thoroughly 
bankment. mixed before placing in the trench. If the 

sewer is of concrete flanges of the same material may be 
built around the barrel at intervals; or the flanges may be of 
stone masonry, water-tight, with rough face. The flange, 
whether of iron, concrete, or stone, is better the rougher it 
is. It would be well to imbed rough stones in the entire 
outside of a concrete sewer under a canal to prevent the 
water following the surface and creating a leak. 

If the earth over the sewer in the canal-bed is shallow or 
is not absolutely impervious there must be sufficient weight 
in or attached to the sewer to prevent it from floating if 
empty. A 24-inch iron-pipe crossing only two or three feet 
under a canal has been known to break in two at a joint and 
a part of it rise through the thin earth covering into the water 
above on account of the hydrostatic pressure brought to bear 
by seepage-water. It must be remembered that an empty 
iron pipe 36 inches diameter, for instance, to weigh as much 
as the displaced water must be if inches thick. Conse¬ 
quently the heavier weights of iron pipe should be used, or 
else they should be weighted down with concrete, iron cast- 











PRACTICAL SEWER CONSTRUCTION. 339 

ings, or in some other way. It will usually be found cheaper 
to use the heavy pipe. 

If it is necessary to pass a sewer under a body of water in 
tunnel this may require the use of compressed air, shields, 
etc., and should not be undertaken without the advice of an 
expert in such work. 


PART III. 

MAINTENANCE. 


I 


CHAPTER XIV. 

HOUSE-CONNECTIONS AND -DRAINAGE. 

Art. 81. Necessity for Intelligent Maintenance. 

It is the too general rule that when a city has constructed 
a system of sewers it considers its duty done, and permits any 
kind of connection to be made with them, by anybody and in 
any way, and takes no more thought of its sewers until com¬ 
pelled to do so by some obnoxious conditions therein. This 
is all totally wrong, and even criminal. While it is not 
probable that any well-designed and constructed sewerage 
system will ever become “ worse than no system at all ” or 
an “ elongated cesspool,” it will not work at its best efficiency 
and free from objectionable conditions if unattended to, any 
more than would any mechanism. 

Moreover, a considerable expense has been incurred to 
provide sanitary sewerage for the citizens, but if careless or 
penurious landlords or plumbers or ignorant householders are 
permitted to construct between the sewer and the house, or 
in the latter, cheap and unsanitary house-connections, -drains, 
and plumbing fixtures the health of the citizens is endangered 

340 





HOUSE-CONNECTIONS AND - DRAINAGE . 341 

and complete return for the outlay for sewers is not received. 
No dread of paternalism should interfere with the proper per¬ 
formance by the city of its manifest duty to require that all 
“ sanitary ” piping and fixtures throughout the city are sani¬ 
tary, and the sewers should be in the charge of an experienced 
officer who is held responsible for their cleanliness and 
efficiency. 

The first necessity for this oversight will come with the 
connection of the dwellings to the sewers. 

Art. 82 . Requirements of Sanitary House-drainage. 

No house-connections should be attached to a sewer 
except in the presence and under the direction of a city 
inspector and by a party who is under bond to follow the 
city’s regulations for such work. 

No house should be allowed to connect with the sewer 
until its construction is entirely completed, including plaster¬ 
ing and sanitary fixtures, owing to the danger that mortar and 
rubbish may otherwise be admitted to the sewer. 

No connection should be made with a sewer except at a 
branch provided for that purpose. If there should be no 
branch within a short distance one may be inserted in a brick 
sewer by cutting through its wall and building a slant firmly 
in place or, in a pipe sewer, by removing a pipe and inserting 
a branch pipe in its place. If 3-foot lengths of pipe were laid 
in the sewer a few 3-foot lengths of branch pipes may be kept 
on hand for this purpose. (Branch pipes are generally used 
in 2-foot lengths.) To remove a pipe from a sewer it may be 
broken to pieces with a hammer, care being taken not to crack 
the adjacent pipe. Then, with a cold-chisel used with some 
rare, the upper half of the bell facing this opening is broken 
away and likewise the upper half of the bell of the branch 
pipe to be inserted. This is then dropped into place with 


342 


SEWERAGE. 


the branch on the wrong side and revolved, thus bringing to 
the top of the sewer that part of both pipes where the bell is 
wanting. The joint is then made, Portland cement being 
substituted for the missing portions of the bells. 

In breaking the cap or plug out of a sealed branch care 
must be taken not to break'any part of the pipe. If broken 
the pipe should be replaced by a new one, as above. If the 
branch is cracked it may be left in, but should be surrounded 
with rich cement concrete well compacted. 

It is absolutely not permissible to cut a hole into a pipe 
sewer and insert the house-connection therein, as it is almost 
impossible to obtain a junction which will not leak or to 
prevent the connection-pipe from protruding into the sewer. 

The house-connection should never be larger than the 
branch which it enters, but should preferably be smaller. A 
4-inch pipe is large enough for any residence or small hotel 
or, in general, for 90 per cent of all the buildings in most 
cities. On a grade of 1 : 40 it should carry the simultaneous 
discharge of ten or more water-closet flushes, or that of two 
large bath-tubs when emptying themselves in two minutes. 
This connection may be of vitrified clay pipe from the sewer 
to a point 5 or 6 feet outside of the cellar wall. It should be 
laid to as perfect line and grade as was the sewer itself, the 
fall of 1 : 40 being the minimum allowed under any but 
exceptional circumstances. If a uniform grade from the sewer 
to inside the cellar is not obtainable or desirable, or if this 
distance be more than 100 feet, it is advisable to place an in¬ 
spection-hole at the fence-line or at some other convenient 
point (see Plate XI, Fig. 10), the grade and line being straight 
each way from this to both sewer and house. If the pipe 
branches before reaching the house an inspection-hole should 
be placed at the junction. The joints of the house-connection 
should be of cement, and it should be of equally as good 
material as, and laid in every way according to the methods 


HOUSE-CONNECTIONS AND -DRA INAGE. 


343 


used for, the sewer. In made ground or quicksand, or where 
trees are near the pipe, or the latter passes near a well or 
cistern, the connection should be of iron water- or gas-pipe 
(not “ plumbers’ pipe ”) with lead joints. 

From a point 5 or 6 feet outside the building into and 
through this the main pipe should be of iron, and should 
extend vertically to and through the roof, its upper end, down 
to a few feet below the roof, being preferably enlarged some¬ 
what. The top should be at a distance from any chimney 
and above any garret or other windows, and should not be 
furnished with a cowl, quarter- or half-bend, or any other 
device. All fixtures in the house discharge into this pipe, 
the intersections being by means of Y’s and not T’s. 

So far all authorities agree. But the general arrangement 
of traps and ventilation-pipes is a point upon which many of 
them differ. The principal point of difference is as to 
whether the pipe should be furnished with a trap between the 
sewer and the vertical “ soil-pipe.” Most agree that a trap 
should be placed just below each fixture, although a few 
would dispense with this and rely upon one main trap only. 
(See “ The Single Trap System of House Drainage,” Trans¬ 
actions Am. Soc. Civil Engineers, vol. XXV, page 394.) 
Some trap is desirable, if for no other reason than to prevent 
long sticks, bones, knives and forks, and other large articles 
from being carried to the sewer. Most sanitarians would 
ventilate each trap by connecting the end furthest from the 
inlet with a main vent-pipe leading through the roof. 

The object of the main trap, which is generally placed 
just inside the cellar wall, is to exclude the air of the sewer 
from the building. As has been previously stated, however, 
the house-connection and soil pipes are in most cases much 
more foul than the sewer, and the danger lies in them rather 
than in the sewer. The vertical soil-pipe, on account of 
the spraying action of falling water, becomes fouler and is 


344 


SEWERAGE. 


more difficult to clean than almost any other part of a sewer¬ 
age system. Hence the author can see little if any advantage 
in the presence of the main trap; none, certainly, if this be 
not vented on both ends to prevent its seal being forced by 
a compression of the sewer-air due to a sudden discharge into 
the sewer from a near-by connection or some other cause, and 
to prevent a forcing of the traps throughout the house by the 
compression of air in the soil-pipe caused by a considerable 
flush of water from a fixture on the upper floors; also to 
admit fresh air to the house-piping. Many excellent authori¬ 
ties, however, advise the use of the main trap. 

The object of continuing the soil-pipe through the roof is 
to allow the foul air from below to pass upward through it, 
and there seems to be little objection to permitting the purer 
air from the sewer to occasionally take the same course, and 
even perhaps some advantage from its diluting effect. 

Whichever the plan adopted, if the workmanship and 
material are of the best there is probably little danger to be 
feared. If vent-pipes are used on a main trap these should 
terminate at a distance of at least 10 feet from any window or 
door, and in such a manner that they cannot be sealed by 
dirt, snow, ice, or frost collecting around the upper ends from 
the damp sewer-air. 

“ Every trap and dead-space in water-closets must be 
separately vented at the top of the outer bend, the branch 
vents connecting with the main vent,” which should be car¬ 
ried from the lowest trap up through the roof. This prevents 
siphoning of the traps by water plunging down the soil-pipe 
from a higher closet or tub, and offers escape for any foul air 
forming in any of the soil-pipes. 

Authorities agree that water-closets must not be connected 
directly with the water-supply pipes, but should be flushed 
through an intermediate tank or tanks or similar appliance; 
that roof-water leaders should never be connected directly 


HOUSE-CONNECTIONS AND -DRAINAGE. 


345 


with the house-connection pipe without an intermediate trap; 
and that all pipes and sanitary fixtures of whatever kind 
should be everywhere accessible for examination, and should 
not be walled or even boxed in. The water-closets should 
never be placed in rooms not receiving light and air directly 
from outdoors, or at the very least from a large air-shaft, 
through a window having at least 4 or 5 square feet area. 

All piping in and near the house should be of iron. 
Wrought iron with screw-joints is preferable to cast iron. 
The use of lead pipe is not advisable, except in short exposed 
lengths, as it may be punctured by nails or gnawed by rats 
and mice, and is apt to sag into unnecessary running traps. 
Where the pipe passes through the cellar wall this should be 
arched, leaving a space of two or three inches around the 
pipe to prevent the breaking of the pipe by a settlement of 
either it or the wall. 

The house-connection should be suspended upon the side 
walls after entering the cellar, and should never be placed 
under the cellar floor, unless, when this is unavoidable, it be 
placed in a shallow trench having brick or stone walls and with 
a removable top forming part of the cellar floor. The soil- 
pipe should have only easy curves and Y’s, no angles or T’s 
anywhere. 

Water-closet tanks should discharge not less than 5 gallons 
with each flush, the pipes leading from these to the closets 
being not less than i£ or ij inches. No overflow from any 
cistern, tank, or refrigerator should discharge into any soil- or 
waste-pipe, but into a trapped sink or bowl connected there¬ 
with, the end of the discharge-pipe being at least 3 inches 
above the water in said sink or bowl. There should be no 
wooden wash-tubs or sinks. Grease-traps, if used, should be 
cleaned out once a week. No ‘‘bell trap” or removable 
strainer should be placed in sinks or tubs. All iron pipes 
used as drains or soil-pipes should be coated inside and out 


346 


SEWERAGE. 


with coal-tar varnish, or asphalt, or better still with enamel. 
A hand- and inspection-hole should be placed in the house- 
connection just inside the cellar wall, and outside the main 
trap if one be used. 

Every system of house-drains and soil-pipes should be 
tested by water-pressure to at least io pounds before being 
accepted or used. (See also ‘‘ House Drainage and Sanitary 
Plumbing,” and “ Sanitary Engineering,” by Wm. P. 
Gerhard.) 

To insure that the above requirements are met by every 
system of house-drainage—and this should be insured—regula¬ 
tions embodying them, and such others as are thought desir¬ 
able, should be drawn up, and an inspector or inspectors 
appointed to examine and approve of all plans for house- 
drainage and to see that these are faithfully carried out. 


CHAPTER XV. 


SEWER MAINTENANCE. 

Art. 83. Requirements of Proper Maintenance. 

The requirements for keeping a sewerage system in good 
running order can be concisely stated as— preventing and 
removing deposits, and maintaining ample and safe ventila¬ 
tion. 

As previously stated, the main dependence for preventing 
deposits is flushing. If a deposit remains for any time it is 
apt to continually increase and become more difficult of 
removal, and deposits should therefore be removed as soon as 
possible after forming. This the automatic flush-tank is sup¬ 
posed to do for 800 to 1000 feet below it, but any forming 
below this limit will probably need to be removed by hand¬ 
flushing from a manhole or by the use of special appliances. 
If deposits continually form in any one place and are not 
apparently occasioned by articles which should not be intro¬ 
duced into the sewer it may be advisable to place a flush-tank 
at the head of where such deposits form, at one side of the 
sewer, but connected with it at a manhole or by a Y branch. 
If obstructions are frequently formed at any one place by the 
introduction of improper matters, such as ashes, bones, etc., 
the source of these should be ascertained and the parties 
responsible therefor punished. 

It should not be taken for granted that a sewer is working 
properly, but the system should be inspected once a week or 

347 


34 « 


SEWERAGE. 


at least once a fortnight. This may require merely a look 
into each flush-tank to see that it works properly, into each 
inlet or catch-basin to see that it is clean and the grating 
unobstructed, and into each manhole (the dirt-pan being at 
the same time removed and emptied) to see that the sewage 
is flowing with sufficient velocity and is apparently not 
dammed back by any deposit below. But during the first 
few months of his service the inspector should enter each 
manhole and look through the sewer at each inspection until 
he becomes familiar with its condition of depth and velocity 
of flow when in good order. If there are any considerable 
odors observed about any appurtenance the cause should be 
discovered and removed. This will usually be a large deposit 
or imperfect ventilation, except in the case of catch-basins, 
where it probably means improper or infrequent cleaning. 

The catch-basins should be cleaned after every rainfall. 
There is danger of putrefaction and objectionable odor from 
these if this is not done within two or three days after each 
rain, but this is almost impracticable in large cities, where 
there are one or two on every corner, without the use of an 
enormous number of men and carts, since each cart with three 
men will clean but five to ten catch-basins a day. As an 
example of what is usually done in this line, a large city in 
New England, which is considered to have an excellent 
Department of Public Works, during the entire year of 1890 
cleaned its 1100 catch-basins an average of 1.84 times each. 
It seems almost impossible that these catch-basins could hold 
the heavier matter washed from the streets during six or 
seven months (or if so the small amount contributed by eacl 
storm would have done little harm in the sewer), and the infer¬ 
ence is that a large part of this was not held, but was washed 
into the sewer; also that the catch-basins were in an unsani¬ 
tary condition a large part of the time. When so treated they 
might better be replaced with plain inlets. 


SE IEEE M A IN TEN A NCE. 


349 


A record should be kept of all sewer-inspections, each line 
of sewer and each appurtenance having a record of its own 
showing when it was inspected, its condition, when cleaned, 
what repairs were made to it, with their nature and cost; of 
the frequency of flushing or of the discharge of each automatic 
flush-tank; of the location and date of making each house- 
connection, with all details as to route, size, and grade of 
connection-pipe, cost, by whom ordered, by whom put in (if 
by private contractor). 

The house-drainage is usually supposed to be, but seldom 
is, looked after by the owner. It is exceedingly desirable to 
have a sanitary inspection made of every house by a city 
inspector at intervals of not more than 12 months; but such 
a plan would hardly be favored by most American communi¬ 
ties, but would be looked upon as an impertinence. It is the 
city’s duty, however, to insist upon all owners and tenants 
observing the sanitary regulations as to construction and use 
of house-drainage systems. 

Extensions of the system should of course be made with 
as much care as were the original sewers, and no alterations 
made in the original plans without a careful consideration of 
their effect upon the system as a whole. 

Art. 84. Flushing. 

When automatic flush-tanks are used they should be in¬ 
spected at intervals to insure their regular discharging. . The 
most common failing with siphon-tanks is the trickling over 
of the water into the sewer as fast as it enters the tank after 
it has once reached the level of the top of the bend. Under 
this condition the siphon will never flush. This trickling may 
be due to faulty designing, but is usually caused by a leaking 
joint or blow-hole in the iron siphon at some point, which 
must be corrected. The frequency of discharge is regulated 


35o 


SE WEE A GE. 


by the cock admitting the water. This can be adjusted only 
by actual trial with each tank. It is a good plan to have one 
or more registering reservoir-gauges for use in the flush-tanks 
which will indicate the times of discharge. A simple one, 
but sufficient for this purpose, can be made with a clock¬ 
works actuating a cylinder on which the height of water is 
constantly registered by a pen whpse motion is caused by the 
rise and fall of a float, the pen and a rod from the float being 
attached to opposite ends of a lever with unequal arms, so 
that the path of the pen is but 4 or 5 inches long. Such an 
apparatus left for a day or two in a flush-tank will serve in 
place of frequent visits to it, and can be moved from one to 
another as each is adjusted to the desired frequency of dis¬ 
charge. The waste of water caused by flushing oftener than 
once in eighteen to twenty-four hours is not justified by any 
proportionate advantages. 

Reference has already been made (Art. 47) to flushing 
directly from 2- or 4-inch branches led from the water-main 
into the flush-tank. In using these the valve is ordinarily 
opened to its full extent, or so much as is necessary to main¬ 
tain the height of water in the flush-tank as great as is safe 
for the tank or sewer. It may be left open until such time 
as the water flowing through the manholes below is perfectly 
clean. It will be necessary to use the most solid construction 
in the flush-tank to resist the considerable force with which 
the water leaves the water-pipe. 

Instead of connecting the flush-tank with the water-main 
by a large pipe a small one is sometimes used, and the tank 
filled from this after closing the sewer end, which is then 
opened and the contained water allowed to flush the sewer. 
This method takes much longer than the previous one and 
is consequently more expensive. In some cases the flush-tank 
is filled by hose from the nearest fire-hydrant. 

In some cities the water is conveyed to the flush-tanks in 


SEWER MAINTENANCE. 


351 


carts, and either the tanks filled from these and discharged by 
hand as above, or from the bottom of the cart a large pipe or 
canvas hose is lowered into the flush-tank and connected with 
the end of the sewer, into which the water is discharged under 
a head equal to the elevation of the cart above the sewer. 
In New Haven, Conn., such a cart is used holding 700 gal¬ 
lons, in connection with which an ovoid ball is passed down 
the sewer to assist in the cleansing, its distance from the 
flush-tank being regulated by an attached cord which passes 
up through the sewer and flushing-pipe to the surface. These 
carts are ordinarily used at manholes along the line of the 
sewer rather than at flush-tanks proper. 

Flushing, as has been stated, is seldom effective for more 
than 800 to 1000 feet below the point of entrance of the 
flushing-water. Hence, when automatic tanks are not used 
at the head of every section of such length which requires 
flushing, this is performed at manholes wherever necessary. 
For this purpose outside water may be introduced by carts, 
as just described; or all the openings in a manhole may be 
stopped and the manhole filled by hose, when the plug to the 

down-stream opening is removed and the sewer below 

1 

flushed; or only this opening is closed, and the sewage is 
permitted to back up in the sewer above, when the plug is re¬ 
moved and the sewage performs the flushing. The last method 
is not particularly satisfactory with pipe sewers in most 
instances, since the head obtainable is usually very small and 
the velocity of flush consequently the same, and if the house- 
connection pipes are on a flat grade the sewage may back up 
these to an undesirable height. Deposits also may form while 
the sewage is accumulating, which will not be removed by the 
flush if near the upper end of the dammed sewage, and the 
time required for a sufficient volume of sewage to collect will 
often be considerable and increases directly as the necessity 
for frequent flushing in each case. 


352 


SE WERA GE . 


The plugs used for stopping pipe and small brick sewers 
may have any of a variety of forms. One design is a simple 
conical cork-shaped piece of wood with heavy rubber so fast¬ 
ened around it as to come between it and the inside of the 
sewer when the plug is pushed into place and make a water¬ 
tight joint. Another consists of a solid centre of plank, 
around the edge of which is placed a pneumatic tube similar 
to a bicycle-tire, which is inserted just inside the sewer and 
the tire inflated by a bicycle-pump. These have ropes 
attached by which to draw them out of the sewer when the 
manhole or flush-tank is full, the air being first released from 
the tube of the one last described. 

Another plan, that of bracing a loose frame or hinged gate 
against the end of the sewer in a manhole, is hardly applicable 
to properly constructed systems, where the manhole-channel 
and sewer are continuous, but may be used in a flush-tank 
designed for the purpose. The cover, whether loose or 
hinged, may be held in place by a brace hinged at the middle 
and extending from the cover across the flush-tank to the 
opposite wall. A rope is attached to the hinge of the brace 
and by pulling this when the tank is full the brace folds up 
and releases the cover. 

In large sewers it is generally impracticable and unneces¬ 
sary to dam back the sewage higher than, or even as high as, 
the crown of the sewer, and a dam one half or two thirds the 
height of the sewer is sufficient. This may be made similar 
to those already described, but not filling the entire bore of 
the sewer. Or a “ pocket dam ” may be used. This con¬ 
sists of a bag of tarred canvas having rings around its mouth 
and a rope passing through these long enough to reach 
from the sewer to the surface. Another rope is fastened to 
the bottom of the bag. This bag is filled with water and 
placed in the sewer-invert, being held upright by the rope 
through the rings, and serves as a dam to the sewage. When 


SEWER MAINTENANCE. 


353 


this has raised sufficiently this rope is released, the bag 
collapses and is removed by the rope attached to its bottom. 

In very large sewers flushing, if practised at all, must 
generally be done with sewage, on account of the enormous 
quantity of water required for this purpose. But this prac¬ 
tice is not recommended where sufficient water can be 
obtained. In the case of storm or combined sewers advantage 
should be taken of light rains by damming up the run-off from 
them in the sewers and flushing with this comparatively clean 
water. Heavy storms of course need no assistance in their 
flushing effect. 

To ascertain the height to which water in a large sewer 
has risen in flushing (or at any other time, as during storms) 
an ingenious method, employed at Omaha, Neb., is to drive 
into the wall, 2 inches apart vertically, small iron rods with 
the ends turned up, on each of which rests a cork with a hole 
in its bottom, which can be readily floated off when reached 
by the water. Upright whitewashed sticks placed in the ver¬ 
tical diameter of the sewer have been used for the same 
purpose, but not with perfect success. 7 

Of the above methods of flushing Andrew Rosewater con¬ 
siders the automatic flush-tank the least expensive, the use 
of 4-inch water-pipes with hand-valves next, then the use of 
hose from the hydrants, and the water-cart method the most 
expensive. Cleaning sewers in New Haven by the water-cart 
above described cost $3 to $4 per mile cleaned. One argu¬ 
ment in favor of hand-flushing is that it renders more prob¬ 
able frequent inspection of the system, which will be made at 
the time of flushing; but on the other hand pressure of other 
duties or carelessness may cause longer intervals between 
flushings than is desirable. As a general rule automatic 
tanks should be used on pipe sewers where there is not 
retained by the city a constant force of laborers for mainte¬ 
nance of sewers and streets and similar purposes. In the case 


354 


SE WEE A GE. 


of large brick sewers it is probably best to resort to one of 
the methods of hand-flushing. For pipe-sewer dead-ends in 
cities with a maintenance force automatic appliances are 
desirable, but are in many instances not used. When any 
flushing is done elsewhere than at dead-ends hand-flushing is 
generally resorted to. 

Art. 85. Cleaning. 

The purpose of flushing is to prevent deposits, or rather 
to prevent the accumulation and solidifying of deposits. But 
from the insufficiency or infrequency of flushing this object is 
sometimes not attained; or obstinate obstructions may be 
formed by sticks, stones, or other matter which flushing is not 
expected to remove, and these must be removed by hand or 
some other method. Catch-basins must be cleaned by hand, 
and this should be done frequently. The manhole dirt- 
buckets, also, should be cleaned at intervals. These last are 
merely removed from the manholes and dumped into a cart 
or wheelbarrow. 

The catch-basins are generally cleaned by ordinary 
shovels, the dirt being taken to the surface by a bucket and 
emptied into a cart. Two men and a cart and horse suffice 
for this work. In some cities, and especially when the catch- 
basins are small, the dirt is removed with long- and heavy- 
handled hoes, the blade of the hoe being at right angles to the 
handle and about 8 by io inches in size. These are used 
from the surface through the manhole-opening or that left by 
removing the grating. Catch-basin walls should be thoroughly 
cleaned with a hose and broom and washed with a solution of 
chloride of lime or some deodorizer, but this is seldom done. 
The cost of cleaning a catch-basin will vary probably from 50 
cents to $2 each, depending upon their size, the frequency of 
cleaning, and other special circumstances or conditions; $1.40 


SEWER MAINTENANCE. 


355 


seems to be about the average for large cities. Catch-basins 
at the ends of siphons are difficult to clean, being in most 
cases at the bottom of a shaft containing many feet of water. 
Long-handled hoes may be used, or the siphon may be closed 
and emptied of sewage to permit reaching the catch-basin. 
An apparatus acting on the principle of the steam-siphon 01 
sand-pump is used with success in the Waltham, Mass., 
siphon, emptying the catch-basin or sump without the siphon 
being emptied. The pipe B } Fig. 

34, is lowered into the sump and 
the nozzle is attached to a hose 
from a hydrant. When the water 
is turned on the sand and other 
solid material, mixed with sewage, 
is sucked up through B and dis¬ 
charged through A into the sewer, 
from which it is prevented from 
returning by a temporary dam in the end of the sewer. 

Small sewers are cleaned by flushing when this is possible, 
but in many cases other means must be resorted to. The 
use of “ pills ” is convenient where there are no stones, sticks, 
or other hard materials in the sewer. These are round balls, 
usually of wood, which are floated through the sewer either 
in the sewage or, if there is not enough of this, by flushing 
water. A set of these 2, 3, 4, 5, 7, 9, etc., inches in diameter 
should be kept on hand. When a sewer is to be cleaned the 
smallest pill is floated through from one manhole to the next, 
where it is caught by an assistant; the others are then sent 
through in the order of their sizes until all have passed 
through up to the size one inch smaller than the sewer. 
When any ball reaches a point where the opening is contracted 
by sediment to less than its diameter the ball, which has 
floated and rolled along the top of the sewer, dams up the 
water until it has sufficient head to force its way under the 
















356 


SEWERAGE. 


ball and scour out the sediment. The ball rolls slowly ahead, 
the current washing away the sediment for an inch or two 
under it. If there is a lamp-hole on the line the ball may 
bob up into it, and a man should be stationed there with a 
pole to push the ball down and into the sewer below the 
lamp-hole. If a stone or stick is among the deposit the ball 
may be stopped by it, in which case both stone and ball must 
be removed by another method. The pill cannot be used 
when the sewer is stopped entirely so that there is no flow 
through it. No cord should be fastened to any of these 
round balls, as it is liable to be rolled about them and wedge 
them in the sewer, catch in obstructions, and generally give 
trouble. Ovoid balls, however, are sometimes used with 
cords attached. These do not roll along the top of the sewer, 
and may need to be weighted to prevent the friction between 
them and the sewer top interfering with their motion ahead. 

In place of the pill, particularly in sewers larger than 12 
or 15 inches, a small carriage is sometimes used which travels 
on wheels through the sewer, its front being of such a shape 
as to almost fill its bore except for an inch or two at the 
bottom. Where the sewer is not more than 3 or 4 feet in 
diameter the carriage is usually provided with other wheels 
on top, which are pressed against the sewer-arch by springs. 
This contrivance is hauled through the sewer by a rope, which 
has first been introduced into it by floating through the sewer, 
a piece of wood or cork carrying a cord to the end of which 
the rope is attached. Another rope is fastened to the rear of 
the carriage to haul it back if it strikes an immovable obstruc¬ 
tion. This is a modification, and on a small scale, of the 
method employed for cleaning the Paris sewers, where a plank 
form, similar in shape to and but little smaller than the sewer- 
invert, is carried by a boat or wagon and lowered into the 
sewer as far as necessary to cause a scouring of the deposit. 
The boat or car is carried forward by the water backed up 




S£ WER MA IN TEN A NCE. 357 

behind the scouring-form, which is raised or lowered to the 
proper position by a workman riding in the conveyance. 

These methods all depend upon the scouring action of the 
water and presuppose a passage through the sewer. Other 
contrivances for cleaning a small sewer under such circum- 



Fig. 35. —Disk for Cleaning Sewers. 

stances are based upon the use of main strength to haul the 
material out. Probably the simplest is in the shape of a 
heavy plank disk to which a rope is attached by three short 
light chains fastened to as many bolts through the disk. One 
of these chains is attached at each side and one at the bottom 
of the disk, and their relative lengths are so arranged that 
when all are taut the top of the disk will incline a little away 
from the rope. Upon the other side of the disk, at its top, 
is fastened another rope. By the latter it is pulled a short 
distance into the sewer, lying flat; the other rope is then 
pulled, when the disk rises into an upright position and scrapes 
along the deposit in front of it. It is well not to draw this 
too far into the sewer at once, but to clean only a few feet at 
each trip. The dirt can be scraped to a manhole and there 
removed by buckets. It is awkward pulling in a manhole 
bottom, and it is well to arrange a pulley in a frame, around 
which the rope passes, as also around another pulley at the top 
to permit of a horizontal pull. The lower frame may consist 
of two 4 X 6 or 4 X 8 timbers fastened to each other parallel 
and a short distance apart, between which the pulley turns in 
journals fastened to their under sides, these timbers being 
braced against the inside arch of the sewer and the pulley 
being in the centre of the manhole (see Fig. 36). This 
method can be used where the material is too heavy to be 









358 


SEWERAGE. 


scoured out by pills or similar contrivances, and also as a 
substitute for these. 

In some cases the sewer will be found entirely stopped, so 
that no cord can be got through it, and an opening must be 
forced through. A rod of some kind is used for this purpose. 
Since none longer than 5 feet can be got into the sewer 
through the manhole (unless it be too flexible for efficient 
service) rods of this length made to joint together are gen- 



Fig. 36.—Method of Using Cleaning-disk. 


erally used. These are sometimes lengths of gas-pipe with 
screw-couplings, or in some cities 1- to i^-inch maple rods 
with brass screw-caps fastened to their ends are used. 
These are forced through the obstruction by working them 
back and forth or even by driving with a hammer. When an 
opening is once made it is well to leave the rod in it and 
work it a little back and forth as the sewage flows through 
until the hole is too large to be in danger of immediately 
stopping again, when a pill or cord may be floated through 
and the cleaning completed by one of the above methods. 

A small sewer or sub-drain may also be cleaned by the use 
of hose, as explained in Art. 78. 

In some cases the obstruction may be so obstinate as to 
necessitate the digging up of the sewer. Before doing this 
its exact location should be ascertained by pushing a rod to it 






















SE WER MA IN TEN A NCE. 359 

through the sewer and measuring its length, or by the use of 
mirrors, as previously described. 

For cleaning house-connections, sub-drains, and other 
small pipe which cannot be readily reached the hose is 
excellent, sufficient water being turned through it to make it 
stiff enough to be pushed through the pipe; or rods may be 
used, as for the larger sewers. Instead of a rod the city of 
Waltham, Mass., has used for these cases a length of steam- 
hose filled with sand, a wooden plug being fastened in the 
end of it. This is flexible, but stiff enough for use in a pipe 
only 3 to 5 inches in diameter. 

Even pipe sewers of 18 inches diameter and up can be 
entered for inspection and cleaning by hand. It is reported 
that in Waltham a Hungarian crawled through 850 feet of 
15-inch pipe running 2 \ to 4 inches deep with sewage, there 
being in at least one place not over 9 inches of clear space 
above the deposits and sewage. The author has seen a con¬ 
tractor crawl through 200 feet of 18-inch sewer, and it is 
nothing unusual for a man to pass through almost any length 
of 24-inch pipe. A large stone or a stick wedged across the 
sewer can frequently be removed in this way and the necessity 
for digging up the pipe avoided. 

If the sewer is found to be broken in any place there is 
generally but one thing to do, to dig down to and replace it. 
A sewer which is only cracked or is leaking badly has been 
repaired by inserting inside of it a line of screw-joint pipe as 
large as can be slipped into it, and sealing the space between 
the two at the ends with cement. The substitution of new 
pipe would probably be cheaper in most cases, however. 

When small pipe is only coated or contains but little 
deposit it is sometimes cleaned by the use of a wire brush, just 
the size of the sewer, fixed upon the end of a rod similar to 
those already described. 

The cleaning of sewers large enough to permit a man to 


360 


SEWERAGE. 


work in them needs no special discussion. If they are large 
enough the dirt may be carried to the manhole in a low car 
running on the sewer bottom. In smaller sewers it may be 
shovelled or hoed into a pile at each of two manholes from a 
point midway between them and removed in buckets. 

An inverted siphon may be cleaned as an ordinary sewer, 
after the sewage flow has been diverted to the other siphon- 
pipe or dammed up and the sewage contained in it pumped 
out. 

In 1891 the cleaning of 123 miles of sewers in St. Paul 
cost $6208, or about $50 per mile; labor 20 cents and team 
and driver 30 cents per hour, foreman $4.18 daily. In New 
Haven, Conn., in 1900, removing 275 cu. yds. of material 
from 9269 feet of 3 to 6 foot sewer cost $1097.73 ; labor $2, 
and foreman $2.50 per day. In Altoona, Pa., in 1901, re¬ 
moving 601.4 cu. yds. of shale-gravel, sand, bricks, and 
stones from 6095 feet of 30-inch pipe and 44 X 33-inch brick 
sewer cost $1491 for labor and $302 for tools and materials; 
labor $2.10 per day. The cost of removing stoppages from 
small sewers will probably average about $2 or $3 each. 
The annual cost per mile of keeping a system of pipe sewers 
clean probably varies between $10 and $75 in most cases; it 
should not exceed $10 to $25 for a well-designed and -con¬ 
structed system containing 20 miles or more of sewers, with 
intelligent, economic maintenance, and during some years no 
expense for this purpose may be required. 


CHAPTER XVI. 


THE SEWAGE-TREATMENT PROBLEM. 

Art. 86. Composition of Sewage. 

Being composed of house-wastes and wastes from manu¬ 
facturing processes carried in suspension and solution by- 
water, sewage is found to contain all the matters contained 
in these, either in their original forms, or combined accord¬ 
ing to their affinities into new compounds* or partly decom¬ 
posed into their elements. In either the combination or 
decomposition gases may be formed, and in these and in 
vapors a small percentage of certain elements in the sewage 
may escape to form the “sewage air.” 

Of the various constituents of sewage, a large proportion 
are harmless; some, while in themselves harmless, may form 
compounds which are noxious, or may interfere with the 
purification; others—the organic matters—are offensive and 
dangerous to animal life while undergoing decomposition, in 
which state they are always found in sewage; and of the 
bacteria many are harmless, but an indefinite number are 
fatal to human life. Purely mineral elements and compounds 
are seldom found in sewage in such quantities as to be 
injurious if taken into the stomach. 

Table No. 25 shows the weight in pounds per day of the 
solid and liquid excrements of a mixed population of 100,000, 
and also the same divided by the weight of 100 gallons (the 
assumed per capita water consumption), giving the parts by 

weight per 100,000 which the excrements would contribute 

361 


362 


SE WEE A GE. 


to the sewage. If the consumption is not 100 gallons, 
multiply by 100 and divide by the consumption.* 

Table No. 25. 


AMOUNT OF EXCREMENTAL ORGANIC MATTER IN SEWAGE. 

(From Wolff & Lehmann.) 



1 

Faeces. 


Urine. 


Total. 



Total. 

Organic 

Nitrogen. 

Phospnates. 

Total. 

Organic 

Nitrogen. 

1 

Phosphates. 

Total. 

Organic 

Nitrogen. 

Phosphat s. 

Pounds per day. 

20,000 

294 

413 

257,920 

2311 

1037 

277,920 

2605 

1450 

Parts per 100,000 parts of 
sewage (water consump¬ 
tion 100 gallons per day) 

24.09 

o-35 

0.50 

309*5 

2.77 

1.24 

333.60 

3.12 

1.74 


The total organic and other matters from the average 
household will probably be .00005 to *oooi times the above, 
and will constitute most of the pollution found in the 
sewage, excepting such as may come from tanneries, breweries, 
slaughter-houses, and markets. The principal constituents 
of organic matter are carbon, oxygen, nitrogen, and hydrogen. 
All contain carbon, but all do not contain nitrogen. Those 
containing nitrogen are in general the more liable to putrefy, 
and are regarded as the more objectionable. For this reason 
the quantity of nitrogen and its compounds in sewage is that 
most carefully determined as an indication of the quantity of 
harmful organic matter present. 

The pollution from manufacturing establishments may 
consist of almost any acids, alkalis, or organic matters. A 
carpet, blanket, and cloth mill on the Schuylkill used daily, 
a few years ago, 48,700 pounds of organic matter, including 
18 different substances, 2520 pounds of 21 different acids, 
and 950 pounds of 6 different alkalis. Brass-works discharge 
considerable sulphate of copper, cyanide of potash, and oils; 
the chief waste from iron-works is sulphate of iron; from 


* See also page 430*/. 
































I 




THE SEWAGE-TREATMENT PROBLEM. 363 

paper-mills come filaments of jute, cotton, and other organic 
matters, caustic soda, chloride of lime, and sulphite; in 
woollen-factories the washing of the wool produces large 
amounts of organic wastes, and there are also discharged soda 
alkalis, logwood, fustic, madder, copperas, potash, alum, 
blue vitriol, muriate of tin, and other dye-wastes; from 
cotton-factories come sulphuric, nitric, and muriatic acids, 
chloride of lime, soda, potash, alum, copperas, blue vitriol, 
lime, pearl-ash, stannate of soda, sugar of lead, indigo, 
cutch, sumac, alkali, soda, and various aniline dyes; from 
silk-factories, sericine, or silk gum, soda, and a small amount 
of dyestuffs. Many of the acids and alkalis from factories 
neutralize each other, and the principal objection to these in 
sewage is that they may form insoluble compounds or foul 
gases, or that the acidity of the sewage may interfere with 
the later treatment. In some instances acids discharged 
from brass-works and iron-mills are sufficient in quantity to 
kill the fish in a river, and of course to render it unfit for 
drinking-water. 

The water itself before pollution generally contains little 
organic but some mineral matter. Lime, chlorine, and iron 
are the minerals most commonly found in solution. Sand 
and clay are generally found in suspension in varying quanti¬ 
ties. Copper, zinc, lead, and other metals are sometimes 
found in small quantities. Lime causes the “ hardness” of 
water, which is classified as either “permanent ” or “ tempo¬ 
rary.” The former is caused by calcium sulphate and other 
soluble salts of calcium and magnesium, not carbonates, held 
in solution; such water cannot be materially softened by 
boiling. Temporary hardness is due to carbonates of calcium 
and magnesium; by boiling such water the carbonic acid is 
expelled and the salts become insoluble. 

Chlorine is found in most waters, being washed from the 
soil, or from the air where it has been carried by ocean 


364 


SEWERAGE. 


vapors. It is unobjectionable in the quantities ordinarily 
found, but is significant in sewage for two reasons: first, if 
more than normal in quantity, it is an almost sure indication 
of sewage contamination, and if not more than normal, that 
there has been no sewage contamination; second, it cannot 
be removed from solution and hence remains constant through 
all filtration and other purification processes, thus serving as 
an index of the strength of domestic sewage, whether purified 
or not. The amount of chlorine in a sample of purified 
effluent and in the sewage from which it was derived must be 
practically the same.* To determine pollution from the 
amount of chlorine present it is necessary to know the normal 
amount in the district in question. This ordinarily varies 
with the distance from the ocean, being least in those locali¬ 
ties which the ocean winds must travel farthest to reach; 
excepting, of course, those places where the ground-waters 
are rich in salt, as in west-central New York. Plate XIII 
shows the distribution of chlorine in the normal waters of 
Massachusetts and Connecticut. It is seen to reach a maxi¬ 
mum of 2.42 parts per 100,000 on Cape Cod. 

Iron is to be found in small quantities in most waters, but 
this and other metallic substances have no significance in 
sewage except as they may affect purification. 

The organic and mineral matter in suspension and solution 
in the water before the addition of sewage matters will of 
course be included in that found in the resultant sewage, and 
it is desirable to learn what this amount is. The Naugatuck 
River at Union City, Conn., contained, as extremes, in Sept. 
1897, 6.05 parts per 100,000 of mineral and 2.20 of organic 
matter, 2.00 parts being lime and .42 chlorine; and in April 
1896, but 1.60 of mineral and 1.55 of organic matter; these 

* For some reason not understood the chlorine in effluents from puri¬ 
fication processes is generally a very little lower than that in the crude 
sewage. 





THE SEWAGE-TREATMENT PROBLEM. 


365 



Plate XIII.—Isochlors of Massachusetts and Connecticut. 





















366 


SEWERAGE. 


being fairly average results for New England in a thickly 
populated district. 

The above illustrates in a general way the constitution of 
sewage; but to understand the methods and processes which 
sewage undergoes during purification it is necessary to study 
the chemical conditions and forms in which these matters 
exist in sewage, as well as those in which they generally 
appear in chemical analyses. Average American sewage 
contains about 40 to 60 parts per 100,000 of solids when the 
water consumption is 60 to 70 gallons per capita. Of these 
about 10 to 20 will be in suspension and the remainder in 
solution. The older the sewage and the more it has been 
agitated the greater will be the proportion of solid matter in 
solution. Of those in suspension 3 to 5 parts are mineral and 
7 to 15 are organic; of those in solution 25 or 30 are mineral, 
5 to 10 are organic. Owing to causes already mentioned, as 
well as to the great variations in per capita water consumption 
in different places, any individual sewage may vary greatly 
from the above figures; but they serve to give a general idea 
of the relative proportions. 

1 

The proportions of the various constituents are stated by 
some chemists in parts per hundred thousand; by others in 
parts per million, or, which is practically the same thing, in 
milligrams per liter; others in grains per U. S. gallon; and 
by many English chemists in grains per Imperial gallon. 
The last can be reduced to parts per 100,000 by dividing by 
7 and multiplying by 10; grains per U. S. gallon by dividing 
by 5*8335 and multiplying by 10. In this work parts per 
100,000 will be used unless otherwise stated, this being the 
more common practice in this country and England. 

About 40 ounces per day of human urine is excreted per 
capita, on an average, and 30 ounces of wet faeces (see page 
362). Of the urine about 0.337 grains are common salt, 0.2 
being chlorine. In the excrements occurs the great bulk of 
the nitrogen found in sewage, mostly as albuminous com- 


THE SEWAGE-TREATMENT PROBLEM. 367 

pounds. This leaves the body in the form of urea, of which 

the composition is CO j It is quickly attacked by 

either the bacillus ureae or micrococcus ureae, or both. Each 
of these, breaking down the urea, convert it into carbonate of 
ammonia thus: 

Urea. Water. Carbonate of ammonia. 

co {S3; + 2 ( H >°) = (nh,),co,. 

“ If the sewage is kept without undergoing purification 
for a day or so, it undergoes putrefaction and begins to give 
off foul emanations; in the course of two or three days the 
albuminous matters begin to split up, and the sewage, par¬ 
ticularly when the water contains sulphates, yields sulphu¬ 
retted hydrogen, which is known by its characteristic odor of 
rotten eggs. When this gas is formed the sewage becomes 
black. As the above changes take place, more and more of 
the solid matter enters into solution, and the sewage becomes 
proportionately more difficult to treat, at any rate by a pre¬ 
cipitation process/’ (Barwise, “ Purification of Sewage/’) 

Vegetable refuse occasions much of the foulness of stale 
sewage, largely because of the sulphur it contains. Putrefac¬ 
tion is preceded by the combination of part of the nitrogen 
and carbon with all the free oxygen and with part of that 
contained in the nitrates. 

It is evident that the form under which the nitrogen is 
found will depend to a considerable degree upon the amount 
of decomposition which the organic matter has undergone. 
This decomposition is facilitated by comminution of the 
particles in suspension, such as occurs in pumping, and 
increases with time, and its character is determined by the 
amount of oxygen contained in the sewage water. In a short 
time after entering the sewers sewage ordinarily contains no 
dissolved oxygen and no nitrogen in the form of nitrates; 
although when fresh it contains some free oxygen and gener¬ 
ally nitrates and nitrites. 


3 68 


SE JVEEA GE. 


Sewage contains countless numbers of bacteria of many 
varieties, as many as 30,000,000 in a cubic centimeter having 
been estimated, of 200 or more varieties. One of the most 
common is the Bacillus coli communis, which originates in 
the animal intestine. Most of these bacteria are harmless; 
many are beneficial in breaking down complex organic com¬ 
pounds and assisting in the oxidation of the sewage; but a 
few are the cause of disease if taken into the human system. 
Among the last are the bacterium of cholera (Spirillum 
cholerae asiaticae) and that of typhoid fever (Bacillus typhosus). 
B. coli communis and B. enteritidis sporogenes are the bac¬ 
teria most easily identified as directly derived from sewage. 
The former is most abundant in sewage-polluted water; the 
latter is not so abundant, but is much more probably patho¬ 
genic, being a possible cause of acute diarrhoea. There are 
also present in sewage large numbers of enzymes, lifeless 
organic substances which exert chemical action in breaking 
down complicated organic molecules. Such are pepsin, pan- 
creatin, and other digestive ferments. Their mode of action 
is not well understood. 

Art. 87. Sewage Analyses. 

If sewage be heated in a platinum dish until evaporated, 
a solid residue is left, composed of mineral and organic 
matter. If this be weighed and then heated to a low red 
heat, the organic matter will be almost entirely burned up, 
while the mineral will be but little if at all changed. The 
difference in weight before and after burning will be almost 
exactly the amount of organic matter in the sewage. The 
first amount is generally called “residue on evaporation ” or 
“total solids”; the burned part, “loss on ignition” or 
“ organic residue” and the unburned part the “ fixed resi¬ 
due ” or “mineral residue.” If a sample of the raw sewage 


THE SEWAGE-TREATMENT PROBLEM. 


369 


be filtered through fine filter-paper, that in suspension will 
be intercepted, and the difference between this and the total 
amount of solids will give the amount in solution. If each of 
these be heated so as to burn the organic matter, the amount 
of this in suspension and that in solution are ascertained. 

Organic matter, as it decays, gives off carbonic acid, 
which in part remains in solution and in part escapes. The 
ammonia resulting from the decay is taken into solution. 
Other organic matter, about ready to decay, gives up 
ammonia when the sewage is boiled. The ammonia in solu¬ 
tion, and the ammonia thus set free from the organic matter 
in the sewage, pass off in the steam in a short boiling; and 
if this steam be again condensed, the ammonia is all held in 
solution and its quantity can be readily determined. This is 
the quantity of ammonia called “ free ammonia,” and, being 
the product of decay, is the most characteristic ingredient of 
stale sewage. “ Free ammonia” is not chemically “ free,” 
but is generally in combination with carbonic and organic 
acids, or even appears as chloride or sulphate of ammonia. 

There is still a quantity of combined nitrogen in the 
remaining organic matter, called “organic nitrogen,” about 
two-sevenths of which can be made to pass off as ammonia 
by putting into the sewage an alkaline solution of perman¬ 
ganate of potash—a strong oxidizing agent—and again boil¬ 
ing, the ammonia thus obtained being called “ albuminoid ” 
or “organic ammonia.” Albuminoid ammonia is being 
constantly changed by decomposition into free ammonia, and 
hence the older the sewage is the greater the proportion of 
the latter to the former. When comparing two samples of 
sewage by their ammonias we must remember that free 
ammonia is largely the result of decomposition of that pre¬ 
viously, but not now, existing as organic matter 

In oxidation, upon which sewage purification largely 
depends, nitric acid is formed from the nitrogen of the 


370 SEWERAGE. 

ammonia and of the organic matter and the oxygen of the 
air. This strong acid immediately combines with the potash, 
soda, lime, or other base in the sewage, forming nitrates of 
potash, soda, etc., which are entirely harmless in the quanti¬ 
ties found in the strongest sewage effluent. The nitrogen 
contained in these salts is called “nitrogen as nitrates” or 
“as nitrites,” or simply “nitrates” and “nitrites”; the 
nitrites being nitrous acid salts in which the oxidation is 
carried less far than in the nitrates owing to lack of oxygen. 
(Nitrites are also formed by the combination of nitrates and 
unoxidized matter, the former sharing its oxygen with the 
latter.) This is probably the most important chemical de¬ 
termination made of sewage. The organic matter may vary 
from 3 to ioo parts of sewage. It would be unusual to find 
as much as .01 part of nitrogen as nitrates or nitrites in 
sewage; but in the effluent or purified sewage as much as 5 
or 6 parts may be found. 

Some analysts determine the amount of oxygen absorbed 
from permanganate, calling this “required oxygen.” This 
test is rapidly and easily made, but measures carbon rather 
than nitrogen, and is adapted to rough comparisons only. 
Table No. 26 gives the analyses of the sewage of several cities. 

As an illustration of the chemical effect of purification by 
oxidation, the Lawrence sewage is seen to lose by filtration 
89of the organic matter (“loss on ignition”). The free 
and albuminoid ammonia is reduced 99.1$, most of that lost 
appearing as nitrates in the effluent. The chlorine is practi¬ 
cally unchanged, as it should be. The bacteria are reduced 
99 - 97 $- 

In the Meriden sewage is seen the effect of dilution in the 
decreased chlorine. If the ground-water contained 0.2 parts 
of chlorine and the sewage 45.8, there would appear to be in 
the effluent analyzed about 45$ as much ground-water as true 
sewage effluent. The true amount of purification would 


ANALYSES OF SEWAGE OF SEVERAL CITIES 


THE SEWAGE-TREATMENT PROBLEM. 


CA 

M 

u 

a 

Q 

V 

Pi 


P 

o 

1 m 

V 

£ 

V 
CA 
•*-» 
a 

cs 

0) 

H 


V 

be 

ca 

£ 

CO 


T 3 

C 

CA 


C 

0/ 

a 

*c 

4/ 

a 

x 

<u 

a 

o 

1 m 


Cm 

V 

p 

E 

w 


u 

13 

> 


O 

Oj 

a 

u 

0/ 

s 

u 

a; 

■«-» 

£ 

>n 


v 

be 

a 

* 

<v 

CA 

JP 

C/3 

0/ 


U to 


p 

o 

1 m 

0/ 

£ 

ID 

CA 


03 

be 

& 

43 

CO 


<u 

two 

rt 

£ 

43 

co 


two 

ai 

£ 

03 

CO 


& 

o 

In 

to 


T3 

C . 

P u 

o v 

u s 

bo? 

6 * 

O T3 
« C 
rt 3 
u o 
X u 
<C bfi • 

. tn 1- ? 

B'xi'z. 

o , 

o V. 

C o 

03 co 03 

w ■%< 


•J 353 UII 1 U 33 

oiqn^ jad BuajOBg 


o 

to 


O 

O 

<D 

O 

to 

on 


to 

On 


CA 

Ctf 

c 

03 

te 

o 


"S 91 IJ 1 IN 


CM 

o 


o 

M 

o 




to 

o 


o 

W 

o 


O' to 

"'*■ M 

O to 

o 


• 3 uuo[q 3 


o 

CO 


o 

00 


O' 


o 

CO 


CO 

oo co 

to « vo 


.2 

‘5 

o 

a 

a 

< 


•urns 

''t* 

00 

M 

CO 

CO 

M 

CM 

0 

.0121 

00 

tr> 

to 

00 

CM 

H 

0 

CO 

00 

8 

On 

M 


CM 

CM 



CO 

to 

d 

M 


d 

•piouiranqiv 

Os 

VO 

O 

CO 

VO 

M 

0 

0 

M 

o 

00 

M 

to 

0 

00 

M 

to 

oo 

VO 

8 

CM 

o 

M 


d 

o 



M 

H 

d 

o 


o 

•33JJ 

to 

M 

CM 

o 

8 

''f 

M 

8 

VO 

o 

to 

to 

to 

M 

to 

00 

VO 

8 

o 


CM 

M 



CM 


o 

o 




c 

o 

43 

P 

T 3 


CA 


I 

ci 

O c 

ag 

> <-* 




00 


VO 

VO 


CM 

CO 


•uoijiuSj 

UO SSO'J 


to 

to 


o 

to 


O' 

N 


VO 

On 


VO 


*3UUO[l{3 t^UUO^I 


to 


o 


o 

CO 


•uoudcnnsuo3 


o 

oo 


CM 

VO 


On 0 
tO 00 


00 


•uoireindod 


00 

to 

VO 





to 

to 

VO 

■N? 

oo 


0 

co 

00 

w 

w 






00 

CM 


00 


U 

V>H 

o 

V 

S 

« 

2 


CA 

CA 


a 

o 

♦-» 

CA 

o 

to 


o 

On 

00 


CA 

CA 

rt 


v 

u 

c 

43 

Im 

is 

cti 

J 


00 

On m 
00 


CA 

CA 


u 

V 
«-» 
CA 

V 

a 

o 


c 

c 

o 

U 

c 

V 

•o 

‘C 

V 

s 


hi 

o 

> 

5 


c« 

</> 

(A 

rt 

&H 


v 9 

























































372 


SEWERAGE. 


therefore probably be shown if each quantitative determina¬ 
tion for the effluent, diminished by 30$ of the amount of the 
same substance found in normal ground-water, be multiplied 
by about 1.45. 

It appears from analyses 5 and 6 that the free ammonia 
in sewage increased during its flow through the sewers at the 
expense of the albuminoid. Also that the number of bacteria 
was practically doubled. It is believed that this increase in 
this and in all sewage is of non-pathogenic bacteria only, 
since sewage appears to be an unfavorable breeding-place for 
the pathogenic varieties. 

The result of a bacterial analysis is generally stated as a 
certain number of bacteria per cubic centimeter. This num¬ 
ber frequently runs up into the millions, of which it is evident 
that no direct count could have been made. To obtain practi¬ 
cable conditions a small amount of sewage is diluted with IOOO 
to 100,000 times its volume of sterile water, and the number 
of bacteria found in this mixture per cubic centimeter is mul¬ 
tiplied by the proportion of dilution. How many of the 
bacteria are pathogenic it is impossible to say with our present 
knowledge of bacteriology and methods of analyzing; for the 
finding of the bacterium of typhoid fever or cholera in sewage 
is an unusual occurrence, so few are they in comparison with 
the total number present. If there was one such bacterium 
in each cubic centimeter of a given sewage, and this was di¬ 
luted 10,000 times for analysis, the chance of this bacterium 
being present in the analyzed sample would be but one in ten 
thousand; but if this sewage be discharged into 50 times its 
volume of water, each glassful of this would be likely to con¬ 
tain five or six typhoid bacilli. It is therefore apparent that 
the absence of pathogenic bacteria from an analyzed sample 
by no means indicates that they are not present in the sewage 
in great numbers. This is of little importance in an analysis 
of sewage, since it should be assumed that the excreta of a 


/ 


THE SEWAGE TREATMENT PROBLEM. 373 

typhoid patient containing millions of these may at any time 
enter the sewer. It is desirable, however, to learn to what 
extent such bacteria are removed by purification or otherwise, 
and on this point there is still great uncertainty. But it is in 
general assumed that any reduction in the total number of 
bacteria is at least no greater than that in the number of 
pathogenic ones in proportion to the number originally 
present. It is now thought that liquefying organisms have a 
germicidal effect upon typhoid bacilli; and also that the latter 
increase in number in sewage but slowly, if at all; conse¬ 
quently that they disappear even more rapidly than a general 
analysis would indicate. 

It is desirable to distinguish between aerobic, anaerobic, 
and facultative bacteria (see page 398), and between the 
liquefying and non-liquefying; largely because of the effect of 
these in the decomposition and purification of sewage. Also 
to ascertain the presence or absence of B. coli communis, 
especially in the case of a stream in which the presence of 
sewage is suspected, since these are considered almost positive 
proof of such pollution. 

The incubator test of purified effluent and of diluted sew¬ 
age has come into prominence in the past two or three years, 
notably through the Manchester (England) investigation of 
sewage purification. This test consists of determining the 
oxygen absorbed by a sample ; then completely filling a bottle 
with the same and placing it in an incubator at 8o° F. for five 
days; after which it is again tested for oxygen absorbed. 
Increase in this is an indication of putrefaction during incuba¬ 
tion; but if the sample has remained sweet there will be a 
somewhat less amount of oxygen absorbed after incubation. 
An effluent or diluted sewage which remains sweet after this 
test is in no danger of further putrefaction—that is, will not 
create a nuisance—unless further polluted. This test is not 
applicable to effluents discharged into streams to be after¬ 
wards used for water-supplies. 


374 


SEWERAGE. 


Art. 88. Aims of Treatment. 

The aim of any treatment of sewage may be either to 
prevent the creation of a nuisance or to produce an effluent 
which, if discharged into a river, will not render it unsuitable 
for city supplies. The former case may exist where the 
sewage is discharged into a river, a lake, or a salt-water bay; 
the latter where into potable fresh water only. The purifica¬ 
tion must be considered from both the chemical and bacteri¬ 
ological sides. For either of the above cases a standard of 
purity is most difficult to decide upon, although many stand¬ 
ards have been advanced. 

, i 

Where it is desired only to prevent a nuisance the bacteri¬ 
ological condition need hardly be considered, unless oysters 
or other shell-fish are reached by the effluent. In such a case 
also the purification need be carried to such a point only that 
all matters in suspension are removed and danger of future 

f 

putrefaction averted. 

The maintaining of a river-water potable, however, calls 
for a much higher standard. To be perfectly safe it would 
seem, from our present knowledge, that all bacteria should be 
removed, since we are not certain that some of those escaping 
are not pathogenic. (See also Art. 12.) The removal of 
99.98$ of the bacteria, however, probably reduces the chance 
of infection by at least that amount: and if the effluent be 
then diluted with ten times its volume of pure water, the 
chance of infection by drinking such dilution would be but 
one fifty-thousandth that by drinking the sewage. The only 
standard for the permissible number of bacteria in sewage 
effluents is—the least possible. It may be possible to sterilize 
sewage, but since bacteria are necessary for the liquefying and 
oxidation of organic matter in the sewage, this would mean 
only a temporary delay in decomposing such matter, and 


THE SEWAGE-TREATMENT PROBLEM. 


375 


would leave it and the poisonous by-products of putrefaction 
to create a nuisance and to produce enteric diseases. This 
might be avoided by completely sterilizing (if such a thing is 
practicable) the effluent from a process by which a sufficient 
percentage of the organic impurities have been removed to 
permit of complete oxidation by dilution. But sterilizing to 
avoid decomposition should not be attempted, since decompo¬ 
sition must precede any purification, and in most cases the 
sooner it occurs the better. It need not involve the giving 
off of noxious vapors or odors, if proceeding in the presence 
of sufficient oxygen. 

Several chemical standards have been suggested. The 
Rivers Pollution Commission (England) in 1868 recommended 
as a limit for effluents discharged into streams: 

Total suspended matter. 4.0 parts 

Organic suspended matter. 1.0 

“ carbon. 2.0 “ 

“ nitrogen. 0.3 

Barwise recommends: 

Total suspended matter.less than 3.0 parts 

Oxygen absorbed at 8o° Fahr. in 4 hours.... “ “ 1.5 “ 

Albuminoid ammonia .0.15 parts 

Nitrogen as nitrates to be at least.0.25 

Mr. F. P. Stearns has given .0080 parts of albuminoid 
and .0399 of free ammonia as quantities below which nuisances 
have not been known to result, and .0233 parts of albuminoid 
and .1116 of free ammonia as limits above which nuisances 
will be created, if the pollution be from sewage. If the 
impurities are of a more stable character, it is possible that 
these limits may be exceeded. Most authorities consider, 
however, that no general standard can be set for all effluents. 

The standards given are for prevention of nuisance only. 

* 

Any standard, however, which does not take into account the 
condition of the stream into which the effluent is to discharge, 


( 










376 


SEWERAGE. 


is incomplete. A more reliable rule would be to ascertain the 
amount of free oxygen in the diluting stream passing the 
effluent outlet per second, and to permit no more unoxidized 
organic matter to reach such stream per second than can be 
fully oxidized by one-half to three-fourths of this amount of 
oxygen (since the intermingling of sewage and stream probably 
will not be complete). So far as all organic matter except 
bacteria is concerned, the above standard would also insure a 
safe potable water if time and opportunity for complete inter¬ 
mingling and oxidation be afforded. 

It should be remembered that the presence of chlorine in 
excess of the local normal is generally an indication of past 
sewage pollution; nitrates indicate the amount of organic 
matter rendered innocuous; and albuminoid ammonia is taken 
as an index of the polluting organic matters still present. 
The character of an effluent should not be judged alone by 
its appearance, by its chemical or its bacteriological analyses, 
but by all three combined; since it may be clear, but contain 
many pathogenic bacteria, or dissolved matter which may be 
precipitated or putrefy and create a nuisance; also a turbid 
effluent may contain only mineral matters or such organic 
ones as will undergo no change but oxidation. 



CHAPTER XVII. 

PREVENTION OF NUISANCE. 

Art. 89. Clarification. 

By clarification is meant the removing of the matters in 
suspension, as is done in the laboratory by use of filter-paper. 
Clarification alone is suitable treatment only when the effluent 
is discharged into tidal waters, or into large streams contain¬ 
ing considerable oxygen but whose waters are not potable. 
It is in most cases desirable, however, to make partial clarifi¬ 
cation preliminary to any purification process. 

Clarification is ordinarily effected by either sedimentation 
or straining or both. The author knows of but two plants in 
this country which have relied solely upon clarification: 
Leadville, Col., which strained its sewage through gravel and 
sand; and Atlantic City, N. J., which used sand or hay as a 
straining material. In either of these, nitrification would 
effect a more complete purification were the quantity of 
sewage which is treated much smaller than it is. 

As a preliminary to further purification sewage is, in the 
majority of cases, strained through screens of wire, or wooden 
slats merely, to remove the coarser particles. A larger per¬ 
centage of these particles can be removed by passing the 
sewage through cage screens, i.e., cages 2 to 4 feet square 
and deep, formed of heavy wire or light iron rods spaced £ to 
I inch apart. At Glasgow a screen of rod-links passing over 
two wheels like a link-belt, and inclined 45 0 with the hori- 


377 


3/8 


SEWERAGE. 


zontal, its lower loop being in the sewage, removes the larger 
matters and raises them to an elevated platform. Mesh 
screens are, however, easier to clean than are these. Screens 
having meshes smaller than \ inch are apt to clog quickly. 
Only the larger matters, such as sticks, paper, rags, leaves, 
etc., are removed by screens. Sewage is sometimes strained 
through coarse coke, gravel, etc., so rapidly and continuously 
as only to clarify and not to purify it. 

A more complete clarification than that effected by screens 
can be produced by sedimentation; that is, the settling of 
matters in suspension to the bottom. If any great degree of 
clarification is to be produced in this way, however, the 
sewage must be quiescent for a considerable time, since much 
of the matter in suspension is but little heavier than water 
and is very finely divided. A part of it is indeed lighter than 
water and floats upon the surface, whence it may be removed; 
or the clarified sewage may be drawn off by a floating arm so 
arranged as to open always a few inches below the surface. 
Besides requiring so much time and capacity of tanks, sedi- 

mentation alone effects but partial clarification, and for these 

1 

reasons it is seldom if ever used unless followed by further 
purification. 


Art. 90 . Precipitation. 

To hasten the sedimentation and render it more thorough, 
as well as to remove a part of the matters in solution, chemi¬ 
cals are in many instances added to the sewage. It was at 

V 

first thought that by chemical precipitation a large part of the 
organic matter in solution could be. rendered insoluble and 
precipitated, and Slater cites over 450 patents granted in 
England for chemicals to be so used. It is now generally 
recognized, however, that practically only the solids in sus¬ 
pension and 5$ to 15 <f> of those in solution can be removed by 
this method. As only about one-fifth of the total solids are 




PREVENTION OF NUISANCE. 379 

in suspension, it is evident that but a small percentage of 
them is removed, although these may include half of the 
organic matter. 

“ The best results that we have obtained by chemical 
precipitation—and we know of no others that are so good— 
leave as much as one-third of the nitrogenous organic matter 
of the sewage in the effluent; this is an abundant food-supply 
for the unlimited growth of a large number of bacteria that 
remain;. . . and, if any of these are disease-producing germs, 
there would be no safety in turning such a liquid into a 
drinking-water stream; and whether it would be advisable to 
turn a liquid containing from one-third to one-half as much 
nitrogenous organic matter as sewage, with abundant bacteria, 
into any stream, would depend upon nearly the same condi¬ 
tions that would attend discharging a less amount of sewage 
into the same stream.” (Report of Mass. State Board of 
Health, 1890.) The organic matter which is not removed is 
in the form of unstable compounds which readily decompose 
under favorable conditions; but such an effluent would not 
be so likely to create a nuisance if discharged into a tidal 
water or large and rapid stream. It would, however, reduce 
the oxygen in said stream, since sewage contains little oxygen 
and acquires none in precipitation. It would also probably 
give rise to the growth of algae—green plants fed by the 
ammonia of the sewage. 

The proportion of organic matter removed by purification 
does not necessarily imply the removal of a proportionate 
amount of food for pathogenic bacteria, since some organic 
matter does not serve such a purpose. That in the effluent 
from precipitation is generally less suitable than that in raw 
sewage; but more so than that in the effluent from filtration, 
during which process, as we shall see, practically all available 
matter has been decomposed by the bacteria in the filter. 

Precipitation is largely or entirely a physical process. 


3&o 


SEWERAGE. 


When lime, for instance, is added to sewage it unites with 
the carbonic acids to form carbonate of lime, and with sul¬ 
phuric acid, if any be present, to form sulphate of lime or 
gypsum; both of which are insoluble in water and settle to 
the bottom of the tank, entangling and carrying down with 
them flocculent matters in suspension. If a large amount of 
lime be used, calcium hydrate instead of carbonate is formed, 
clarifying the sewage. Sufficient lime generally remains in 
solution in the carbonic and other acids to render the sewage 
alkaline. If iron sulphate or aluminum sulphate be added to 
sewage thus made alkaline, a flocculent precipitant of hydrate 
of iron or hydrate of aluminum is formed which seems to 
precipitate slightly more of the soluble matter than does.lime. 
Ferrous sulphate seems to be useless without the addition of 
lime to combine with the excess of carbonic acid and with 
the sulphuric acid of the ferrous sulphate. Ferric sulphate is 
more readily precipitated and more completely insoluble than 
the ferrous salt, and the use of lime with it is not so neces¬ 
sary; as is also the case with aluminum sulphate or crude 
alum, ordinary sewage containing enough alkali to decompose 
these salts. It is found that if more lime is used than will 
combine with the carbonic acid in the sewage, no benefits 
result from the additional lime; and the free lime is objec¬ 
tionable because of the danger that it will kill fish in the 
water reached by the effluent, and that it will cause a 
secondary precipitation in the effluent or stream which 
receives it. With ferric and alum salts, however, the precipi¬ 
tation increases with the amount used, though at a less rate 
after a certain point is reached. 

With Lawrence, Mass., sewage 1600 to 1800 pounds of 
lime per 1,000,000 gallons of sewage gave the best results; 
as is illustrated in the following table from the Report of the 
Massachusetts State Board of Health for 1890. 


PREVENTION OF NUISANCE. 


381 


Table No. 27 . 

RESULTS OF THE TREATMENT OF SEWAGE WITH DIFFERENT 

AMOUNTS OF LIME. 

(By Mass. State Board of Health, October, 1889.) 



Turbidity. 

Total Solids. 

Loss on Ignition. 

Fixed Residue. 

Free Ammonia. 

Albuminoid 

Ammonia. 

Chlorine. 

Acid Number 

Phenolphthalein. 

Alkalinity. 

Precipitated 

Calcium 

Carbonate. 

Original sewage . 

.50 

^ 4 . . O 





523 

-.07 

• 3 1 


Filtered through paper . 

42 . 8 

I "2 . 2 

29 . 6 

2. n 

0.28 


After settling one hour. . ... 

•30 

44.8 

16.0 

28.8 

M 1 

O < 
0 

o -45 

5.22 

— .06 

• 3 ° 

I 

Effluent with 500 lbs. of lime 











per 1,000,000 gals.of sewage 

.27 

51.2 

16.8 

34 4 

1.90 

o -34 

5.20 

-f .05 

• 44 

I 

Effluent with 800 lbs. of lime 

•25 

55 -o 

14.8 

40.2 

2.00 

0-34 

5.20 

+ • x 4 

•S 2 

I 

“ “ 1000 “ “ “ 

.19 

50.2 

12.8 

37-4 

2.00 

0.32 

5.16 

. 20 

.56 

4 

“ “ 1300 “ “ “ 

•13 

5 1 -6 

11.6 

40.0 

1 • 75 

0.26 

5- x 4 

-f - 2 5 

•56 

8 

“ “ 1600 “ “ “ 

• x 4 

48.8 

10.8 

38.8 

1.85 

0.25 

5-05 

4 -.25 

•47 

l6 

“ “ 2000 “ “ “ 

• T 5 

53-6 

11.0 

42.6 

1 -75 

0.27 

5-09 

+ • 3 ° 

• 49 

*9 


The use of 1600 to 1800 pounds of lime also removed 
from 99.2$ to 99.5$ of the bacteria. By the use of 1000 
pounds of ferrous sulphate with lime 98$ of the bacteria were 
removed. By using 400 pounds of ferric sulphate 95^ were 
removed; and by the use of 1000 pounds of alum from 83$ to 
99^ were removed. The removal of bacteria is due in part 
to the mechanical action of the precipitate carrying them 
down, and in part to the chemical action of the precipitant 
in killing them. 

Dibden, in an examination of 575 effluents obtained by 
using various chemicals, found the best results to be obtained 
with 140 parts each of lime and ferrous sulphate, which 
removed 30$ of the soluble organic matter. The best result 
with lime alone was obtained by using 210 parts per 1,000,000, 
which removed 25$ of such matter. Lime and alum, 70 
parts each, removed 18#; and lime, alum, and ferrous sul¬ 
phate, 10,000, 1430, and 7140 parts respectively, removed 
52$ of the soluble organic matter. 

The chemicals above referred to—lime, ferrous and ferric 






























3 82 


SEWERAGE. 


sulphate, and alum—are those most commonly used, chiefly 
because of their cheapness. A few others give good results, 
but the majority of precipitants bearing other names are but 
combinations of these with other more or less beneficial sub¬ 
stances. Some of the best known of these are: 

The ABC process, using alum, blood, clay, and seven 
other materials, alum and clay constituting about 97$ of the 
mixture. 

Alumino-ferric process, using crude alum, with a trace of 
iron salts. 

Amines process, using lime and herring-brine (claims 
sterilization). 

Electrolysis. The sewage is electrolyzed and oxygen 
liberated, which attacks the organic matter and also forms on 
the iron negative-poles iron salts which act as a precipitant. 

Ferrozone, composed of crude alum, ferrous sulphate with 
magnetic oxide, and a few other mineral matters. 

In England in 1894 there were 174 precipitation plants, 
among 60 of which 20 used lime alone, 11 used ferrous sul¬ 
phate (commonly called copperas), 8 used lime, copperas, 
and sulphate of alumina, and 9 used “ ferrozone.” 

The results above quoted are from laboratory experiments. 
Actual practice could hardly be expected to attain as good 
results with the same materials. Table No. 28 on page 381 
shows the results from a number of chemical-disposal plants. 

Excepting the Columbian Exposition plant, at none of 
the above works have more than occasional analyses of 
sewage and effluent been made. Scientific and systematic 
study of the purification effected by chemical treatment has 
been made at few if any European plants, and in this country 
Worcester is the only city which has done this. This city of 
107,000 inhabitants treats its sewage with 1100 pounds of 
lime per 1,000,000 gallons of sewage; the sewage containing 
considerable copperas. Hourly tests of sewage and effluent 


PREVENTION OF NUISANCE 


383 


Table No. 28 . 


RESULTS OF CHEMICAL PRECIPITATION. 


Results at the East Orange chemical-treatment work and filtration- 

grounds. 1893. 


3 grains of lime and 2 of sulphate of alumina used. Contributing population 15,000. Sew¬ 
age per capita, 90 gals, per day, 46 of which was ground-water. 14.7 acres of ground used. 



Ammonia. 

Oxygen required. 

Nitrites. 

Nitrates. 

Chlorine. 

Total Hardness. 

Permanent Hard¬ 
ness. 

Temporary Hard¬ 

ness. 

Total solids. 

Mineral Matter. 

Organic and Vol¬ 

atile Matter. 

Free. 

Albuminoid. 

Raw sewage(estimated) 

1.0-1.5 

.30-70 




5-10 




40-108 

18-91 

7-22 

Effluent from chemical 













treatment. 

.087 

.027 

4.4 

.OO 

.26 

6.12 

15.6 

3.00 

12.60 

29.6 

2 3*5 

6.1 

Do. followed by land 













filtration. 

.02 

.003 

4.0 

.OO 

.38 

4.0 

20.0 

12.5 

8.50 

25-5 

22.0 

3-5 


Glasgow (Scotland) chemical-treatment works. 


Raw sewage 
Effluent. 


2.05 

.6l 

4.91 






38.0 

138.0 

95-7 

2-45 

•34 

1.03 






32.8 

65.2 

57.2 


42.3 

8.0 


Columbian Exposition (Chicago). 1893. 

Lime, ferrous sulphate, and alum. 

5.84 
4.72 


Average sewage.. 
Average effluent. 


. 884 
■438 


.806 

• 450 


3.036 

1.646 


5-59 

5-24 


Chautauqua, N. Y., 1893. 


3000 population; 42 gals, per capita of sewage, 22 of which is ground-water. 15 grains of 
lime, 2J of alum, and i of copperas per gallon. 


Sewage . 

2.428 

2.088 




6.013 




I 17 .O 

CQ - 2 

47 .8 

Effluent. 

1-357 

0.486 

. 


.... 

6.013 

.... 

.... 

. 

23.6 

14.4 

9.2 


have been made since July 1893, with the following average 

* 

results: 


PERCENTAGE OF ALBUMINOID AMMONIA REMOVED. 


Total. 

Dissolved. 

In Suspension. 

For 1894... 

-50.78 

IO.48 

89-54 

1895... 

. 51-63 

8-43 

91 . II 

1896... 

.. .. 53-92 

15.04 

92.02 

1897... 

. 53-02 

10.75 

93-46 

1898... 


11.77 

92.62 

Average for 5 years 52.62 

II.29 

91-75 





























































































3^4 


SE WERA GE. 


For the year 1898 the following average results were 
obtained (daily consumption, 63 gallons per capita): 



Ammonia. 

Oxygen 

Consumed. 

Chlorine. 

Free. 

A 

Total. 

| 

lbumino 

Dis¬ 

solved. 

d. 

Sus¬ 

pended 

Unfiltered. 

Filtered. 

Sewage for year ending Dec. i, 1898. 

.851 

•438 

. 221 

.217 

4<°3 

2.17 

4.76 

Effluent “ “ “ “ “ “ 

•775 

.211 

.195 

.016 

2.06 

2.06 

4.81 

Per cent removed. 

8-93 

51.82 

n.77 

92.62 

48.89 

5-07 

-1.05 


The daily sewage samples consist of forty-eight portions taken half 
hourly. Sewage samples are taken as nearly as possible in proportion to 
the amount of sewage being received at the time of sampling. Effluent 
samples consist of twenty-four portions taken hourly. 

Since it takes several hours for sewage to pass through a 
precipitation process, and since the sewage varies greatly from 
hour to hour, analyses of sewage and effluent are comparable 
only when the effluent sample is taken later than the sewage 
sample by the time required for it to pass through the 
process, or when samples of each are taken at frequent equal 
intervals through 48 to 72 hours. To be strictly accurate, the 
amount of each sample should also be proportionate to the 
volume of flow when taken. A sample of sewage and one of 
effluent taken at 9 or 10 P.M might show the latter stronger 
than the former, although considerable purification was really 
being effected. 

A comparison of all available data would indicate that 
under the most intelligent and careful supervision chemical 
treatment will in actual practice remove 85 $ to 95 fo of tne 
suspended organic matter, and 10# to 15# of that in solution; 
or 80$ to 93$ of the total suspended matter, and 50$ to 60$ 
of all organic matter. 

The amount and kind of chemical which is most effective 
for any given case will depend upon the strength and char¬ 
acter of the sewage. This may already contain a large 
























PREVENTION OF NUISANCE . 


3 8 5 


amount of iron or lime, or it may be very acid and require 
more than the ordinary dose of an alkali. The amount of 
lime should be sufficient to make the sewage slightly alkaline, 
as indicated by litmus or phenolphthalein. Commercial lime 
will yield 65$ to 80$ of its weight in calcium oxide; and this 
should be at least equal in quantity to the carbonic acid in 
the sewage. The addition of more than this will increase 
the efficiency of the treatment very little and will give an 
alkaline effluent which is injurious to fish; also the additional 
lime will slowly precipitate out, leaving a deposit on the 
banks and bottom of the stream; and if the effluent is highly 
alkaline, it will not readily nitrify in subsequent filtration. 

At the London disposal works 3.8 grains of lime and 0.88 
grains of copperas are used for each gallon of sewage. At 
East Orange 8 grains of lime and 10 of alum per gallon were 
recommended by the engineer, but only 3 of lime and 2 of 
alum were ordinarily used. At the Mystic Valley treatment 
works about 14^ grains of alum per gallon; at Chautauqua 15 
grains of lime, 2 \ of alum, and J grain of copperas per gallon 
are used (42 gallons of sewage per capita per day). At 
Glasgow the amounts are varied with the character of the 
sewage, the following being their general rule for apportion¬ 
ing in 1899: 























336 


SEWERAGE. 


At Worcester, Mass., where analyses are taken every half- 
hour and great care is used in apportioning the chemicals in 
accordance with the chemical composition of the sewage, 
there was used in 1898 an average of 51^ grains per gallon, 
occasionally reaching 200 grains; the sewage being very acid. 
At several intervals of if to 2 hours’ duration each, during 
every week-day, the sewage contains more than enough 
copperas to act as a precipitant, and this is retained and 
mixed with later sewage which does not contain much iron. 

In Brooklyn (26th Ward) 1 pound of lime is added to each 
1000 gallons of sewage, and of perchloride of iron 1 pound to 
each 3500 gallons. 

For various manufacturing wastes it is often necessary to 
use special chemicals. From a series of experiments con¬ 
tinued through several years the Massachusetts State Board 
of Health finds that all such wastes can be purified, but that 
there are practical difficulties in filtering certain of these 
without previous treatment. Thus, wool waste-liquors should 
be treated with sulphuric acid or calcium chloride or other 
chemical for cutting the fats, lime and copperas having small 
effect on them ; and should be greatly diluted if to- be 
nitrified.* Tannery liquors can be freed of 60$ or more of 
their organic constituents by the use of lime, and can then 
be filtered. The presence of arsenic, as from tanneries or 
paper-works, of sulpho-naphthol, as from tanneries, or of any 
other germicide, will interfere with nitrification unless they 
be removed or formed into insoluble compounds by use of 
chemicals. 

Besides the directly chemical processes there are a few 
which might be called Indirect-Chemical. Those best known 
use electricity for manufacturing the precipitating chemicals 

* Mechanical methods, such as skimming and applying centrifugal 
force, have been used for fats with some success. 



PREVENTION OF NUISANCE. 


3 87 


from the sewage itself, from electrodes, or from salt water. 
The chemicals thus appear in the sewage in their nascent state, 
in which condition they are considered to be most active. 

Sewage has, by the “Webster” process, been decom¬ 
posed by causing it to flow between electrodes placed an inch 
or so apart in a trough, after which it was allowed to settle 
for an hour or two. By this method chlorine and oxygen 
were carried to the positive electrodes as a hypochlorite, at 
the rate of 2 grains per gallon treated. It was estimated 
that it required 0.25 ampere-hours of current for each gallon 
treated. There was effected a 95.3$ reduction of the sus¬ 
pended matter. 

Another process uses electricity to decompose sea-water, 
or a solution of magnesium and sodium chlorides. This is 
an antiseptic, not a purifying process, sodium hypochlorite 
or some oxygenated compound of chlorine being produced. 
This method has been used in this country, under the name 
of the Woolf process, at Brewsters, N. Y., and at Danbury, 
Conn.; but in 1895 the latter place was enjoined from dis¬ 
charging the effluent from this treatment into the Still River 
and is now filtering its sewage. At Brewsters 1000 gallons 
of water containing 160 pounds of salt was subjected to an 
electric current of about 700 amperes and 5 volts, the positive 
electrode being of copper plated with platinum, and the 
negative of carbon; a 4-H.P. dynamo being used. One part 
of this solution was used in 100 parts of sewage; or $3.20 of 
salt to each 1,000,000 gallons. Practically the same process 
was used in Bombay in 1897, but abandoned after four 
months’ trial, it being found that the same amount of free 
chlorine could be obtained in chloride of lime at half the cost. 
\Jp to the present time, at least, it has been found that any 
desired chemicals can be purchased more cheaply than they 
can be manufactured from sewage, whether they be precipi- 
tants or fertilizing precipitates. 


388 


SEWERAGE . 


Art. 91 . Precipitating Plants. 

Considering the practical application of the above ideas, 
we see that we must prepare the chemicals, introduce them 
into the sewage, permit the latter to deposit the insoluble 
matter, draw off the effluent, and dispose of this and of the 
deposit (called ** sludge ”). 

The chemicals are ordinarily obtained as crystals or in 
powdered form. As such they would not readily or quickly 
mix with the sewage, and they are usually dissolved, better 
in sewage than in water, to form a more or less saturated 
solution, in which form they are introduced into the sewage. 
In Glasgow the lime-mixer consists of a cast-iron box, through 
which passes a vertical shaft driven by belting, to the shaft 
being attached four horizontal radial bars at different eleva¬ 
tions and of different lengths. Pieces of chain are used as 
agitators which drag along the bottom to prevent deposit. 
A horizontal grating with 7 X ij-inch spaces fills the interior 
at 2 feet 8 inches from the top, through which grating the 
lime must percolate. The depth of water in the mixers is 
usually 3 feet 3 inches. The alum is mixed in four wooden 
vats 3X5X10 feet, the agitation being effected by exhaust 
air from the sludge-lifts which is led into the bottoms of the 
vats. 

In East Orange the mixers were in the form of cylindrical 
cast-iron vats 4 feet in diameter, with conical bottoms, each 
overlaid with a perforated plate. The chemicals were placed 
on the plates and air blown in from the bottom as in the 
Glasgow plant. 

At Worcester the mixing-tanks are 8 X 16 X 8J feet 
deep, of iron in brick masonry. Two and one-half tons of 
lime can be mixed at a time in each. Compressed air is used 
here also as an agitator. 

The concentrated solution thus prepared is admitted to 


PREVENTION OF NUISANCE. 


389 


the sewage and should be thoroughly mixed with it. This 
should be done before the sewage is pumped, if pumping is 
necessary; both because this assists in the mixing, and 
because less suspended matter in the sewage has been taken 
into solution, in which form but little of it can be removed 
by chemicals. To obtain thorough mixing with the sewage 
it is better to maintain a continuous flow of precipitant than 
to introduce a certain amount at intervals of one to fifteen 
minutes; although the latter is generally the simpler plan. 
The amount of chemical introduced per minute should be 
proportioned to the amount of sewage flowing and to its 
chemical composition. For this purpose analyses should be 
taken about once an hour; and the flow at any moment 
should be ascertainable by observing a weir inserted in the 
sewage channel, or otherwise. A gate or cock can be pro¬ 
vided with an index or gauge by which the amount of chem¬ 
ical required from time to time can be caused to flow into the 
sewage. In very small plants, however, it may be found 
cheaper to introduce the chemical at such a fixed rate during 
the day, and such another during the night, as has been found 
to produce the desired purification with the highest rate of 
flow of the strongest sewage; thus avoiding the expense of 
keeping a chemist constantly on the work. To effect the 
mixing of the chemical and the sewage, the former is generally 
introduced while the latter is flowing along an open channel, 
which is provided lower down with baffle-boards forming a 
“ salmon-ladder,” or with a small under-shot wheel. 

From this channel—after being pumped, if this is neces¬ 
sary _the sewage flows to tanks in which the insoluble matter 

precipitates, forming sludge. There are three general styles 
of tanks: the continuous-flow and the intermittent-flow hori¬ 
zontal tanks and the upright tank. In the intermittent-flow 
one tank is filled and the sewage is then allowed to stand at 
rest for from half an hour to three hours, another tank being 


39° 


SEWERAGE. 


meantime filled. Three tanks at least are here necessary; 
several small ones being better than a few large ones, as 
allowing longer rest for sedimentation with equal storage 
capacity. Since each tank must be emptied of the clarified 
sewage, they must either be pumped out, or the stream or 
land to which the effluent is led must be several feet lower 
than the sewer-outlet. The Glasgow tanks require 7 minutes 
to fill, 45 minutes of rest, and 7 minutes to empty. 

In the continuous-flow tank there is no absolute rest, but 
the sewage is continually moving at a rate of .02 to .006 of a 
foot per second through the tank from inlet to outlet. Two 
tanks only are necessary; and, the effluent leaving but 
slightly lower than the sewage enters, pumping of sewage, 
whidi might be necessary with intermittent tanks, is avoided. 
The cross-section of the continuous tank can be calculated by 
dividing the maximum flow per second in cubic feet by the 
required velocity—.02 to .01. The length will depend upon 
the time the precipitant will require for settling. From 2 to 
8 hours is the more general practice; 2 hours should generally 
be sufficient if based on the maximum flow, for the ordinary 
flow will then have about 4 hours. Upon this basis, if the 
velocity is .02 of a foot per second, a tank 144 feet long will 
be required. The Worcester tanks are i66-§ feet long. 

In some plants the continuous-flow tanks have cross-walls 
over which the sewage is required to flow, but this is by some 
considered harmful rather than beneficial; except that there 
should be such a wall at or near the upper end to reduce 
agitation in the tanks by the entering sewage. 

Tanks must have some arrangement for removing the 
sludge. In intermittent-flow tanks the effluent is generally 
drawn off by a hinged pipe, its free end being maintained, 
by a float, about 3 to 6 inches below the surface. When the 
effluent begins to run cloudy the remaining contents of the 
tank (or the sludge) is drawn off into a sludge-well or pit, to 


PREVENTION OF NUISANCE . 


39 1 


facilitate which the tank bottom slopes to a middle channel, 
which itself slopes toward a sludge-gate. In the continuous- 
flow tanks the sludge may be lifted by a pump whose mov¬ 
able suction passes just above the bottom; or in some cases 
it may be drawn off through an opening in the bottom of the 
tank; the sludge being preferably forced to this opening 
(which is at one end of the tank) by a “ squeegee ” reaching 
across the tank and travelling its full length pushing the 
sludge before it along the bottom, and scraping from the 
sides the colonies of bacteria which are likely to grow there. 
In some cases the supernatant sewage is pumped out before 
the sludge is removed. 

Intermittent-flow tanks have been constructed in this 
country at the Mystic Valley works, and continuous-flow at 
East Orange and Long Branch, N. J., Worcester, Mass., 
New Rochelle, N. Y., and Canton, Ohio. 

Tanks should have smooth walls and should be water¬ 
tight. There is little danger from frost, except in the most 
northern States, as the sewage retains considerable heat and 
the tanks are generally open to the air. The East Orange 
ones were roofed over as a concession to the prejudices of the 
citizens living quite near the works. On account of this 
popular prejudice, as well as to reduce the cost of the con¬ 
siderable area occupied by horizontal tanks, they will generally 
be placed as far as possible from built-up sections. Where 
this cannot be done the area required can be reduced by use 
of a vertical tank. 

In the vertical tank the sewage flows upward and the 
precipitant collects on the bottom, which is, in the “ Dort¬ 
mund ” tank, conical in shape. Fig. 37 shows the Chicago 
vertical-flow tanks, modelled after those at Dortmund. If 
the sludge-pipe is made to discharge to 2 feet below the 
level of the sewage in the tank, this head will be sufficient to 
force it out without pumping, providing it contains 90$ to 


39 2 


SEWERAGE. 


97^ of water, as most sludge does. In this tank, however, 
some sludge is likely to adhere to the sides of the cone, which 
must be cleaned occasionally by hand or by a revolving 
scraper. In the Candy tank* the bottom is flat and the sides 
circular and vertical; and both sides and bottom are cleaned 



Fig. 37. —Elevation and Section of Receiving and Precipitating 

Tanks. 

by a squeegee revolving on a central vertical shaft, the sludge 
being forced into and through a pipe at the bottom by a 
hydrostatic head of 18 inches as just described. In the 
upward-flow tanks the sewage rises at the rate of .005 to .01 
foot per second; and as the precipitant falls at an average 
rate of .02 to .03 foot per second, it slowly reaches the bottom 
of the tank. Experience seems to show, however, that not 


* See Engineering News, December 28, 1899. 






















































































































































































PREVENTION OF NUISANCE. 


393 


quite so large a percentage of organic matter is removed in 
these as in horizontal-flow tanks. Upward-flow tanks are 
particularly adapted to localities where the available space is 
small 

With whatever style of tank, the sludge should be re¬ 
moved at short intervals, since it is liable to decay and affect 
the purity of the effluent, gives off foul gases, and even 
rises in flaky masses to float and putrefy on the surface. In 
a few instances the treated sewage has been run directly onto 
land divided into beds by high embankments, where the liquid 
matter drains off and the sludge, when dry, is raked up.. 
For this purpose large areas are necessary, as the soil quickly 
becomes water-soaked unless given long periods of rest. 

The sludge from precipitation-tanks being only concen¬ 
trated filth, the difficulties of disposal have been merely 
focussed upon a smaller volume of matter, which must still be 
disposed of in some way. There is manurial matter of value 
in this, but no process has yet been found by which it can 
be utilized at a profit, and disposal of the sludge remains the 
problem of this method of treatment. Glasgow sludge con¬ 
tains 4.63$ of organic matter, 5.60$ of mineral matter, and 
89.77$ of water. The table of analyses of English sludges 
on page 394 is taken from Robinson’s “ Sewerage and Sewage 
Disposal.” 

In a few places a small amount of sludge is removed by 
the farmers, but this cannot be relied upon as a method of 
disposal. London maintains six or more sludge ships, each; 
carrying 1000 tons, which carry 300,000,000 gallons of sludge 
daily fifty miles to sea and dump it there. In several places 
in this country the sludge is run onto ‘‘ sludge-beds of 
porous soil, ashes, burnt clay, or sand, through which the 
liquid soaks, leaving a dry deposit like heavy, coarse brown 
paper which can be burned; or is used for filling low lands, 
as at Sheepshead Bay. The drying sludge gives off consider- 


394 


SEWERAGE. 


03 

CM 

• 

O 

2 

w 

hJ 

m 

< 

H 


o 

w 

HH 

fi 

HH 


w 

o 

o 

£ 

.-3 

m 

W 

O 

<J 

£ 

w 

c/3 

ta 

O 

C /3 

W 

C/3 

K* 

►J 

<5 

fc 

<< 

C/3 

•N 

W 

CJ 

u 

t 4 

1-3 

c 

£ 

CA 

A 


c 

£ 

o 

H 

Vi 

o 

e 

« 


u 










O 


o o 

r> p h o> co oo h p 

M 

O 04 CO 


in 

•a 

-a; <V 

r— y 


O oo o u->o co h 


O' vo vO 



c 

r3 o 

HH 

<M 


C4 m M l-H C4 rf 

CO 

M 

• 

M 

5 

®CU 

M 

HH 


04 CO M 

O' 


«o 

HH 

u 


'tsR 










co oo 

HH HH 

VO vO OOP no 

H^ 

-1" CO HI 



C /3 

a 

O' 

Hi 

C4 lO 

04 M -^-O vO CO 

co 

O O CO 



_U 

!j 

W 

CJ 

HI 

VO O W 04 M 04 

O' 

04 HI HI 

• 

HH 

<u 


HH 

04 


HI 04 04 

O' 



04 



ta. 









C 

O 

04 

vn 04 

h h 04 o O 

O 

3-0 t 


04 


O 43 

r T 

O' o 

M vovO CO CO CO 

CO 

vO r^co 




</! ^ 










c P 

O 


M 

coi>t>NO 

6 

M 

• 


C/5 

T3 

K ^ 

HH 

04 


H-l HH 

o 

HH 



HH 

<D 

•o . 









_3 

43 rj 

O 

CJ 

'-}- VO 

04 00 ^ HI ■O- o 

o 

0"0 o 


04 


<n ^ 

VO CO 

vO H-C 

Tf vO VO O O vO 

M 

coo co 




*U CQ 

O . 

O' o 

C4 

CO O' VO rf HI 

o 

HH 






04 


co 

o 

M 



HH 




tR 














O' 1— o hi VO HI 

o 

o o 

O' 

cj 

in 


04 



O 

o 

O 

vo r ^ O vO 

O 

co O 

HH 

vn cj 

m 



lo 

o . 

o 

cn 

04 

vo O 

04 

vo 04 

O' 

HH 

HH 


Is 

H 

Si c 

HH 

04 





O' 



<0 

04 

c 

^ a 

a a 












V 

> 

o 

-fco o 

04 -H-O O 


co co 

O 

O 04 

hh 


O 

CJ 

C/3 

O 

m 

to 

COvO Hi CO 

HH 

HH CO 

04 

*+ O' 

HH 






o 

HH 

HOC' 



o 

en 

HH 

• 

o 



HH 

CJ 




cn 

o 




04 









HH 







■feR 













CJ 

cn 

cn 

■tNC'C' 

HH 

O' CO 

O 

0"0 

o 





O in 


[n N 04 O 

o 

CO CJ 

HH 

in O 

CO 



'U 


o 



HI CO O VO 

04 

co o 

O' 

HH 



in 

o 

aJ 


CO 


HI 04 


HH 

O' 




HH 

Vh 

a 












'O 


'tR 











cS 

£5 

O 

in 

o 

vtOOvO 

HH 

O' o 

co 

-1- 04 

o 

•d 

HH 

03 


O' oo 

O vo 0"O 

HH 

^ co 

in 

1's'O 





oo 

cn 


O O H 

04 

cn hh 

o 

HH 



in 




cn 


HH HH 


04 

o 




HH 









HH 


















r* 

O" co 

CJ 

hi O O vO co 

I'' o 

O 

in hh 


>s 


o 

4-1 

B’SS 

CO 

HH 

VO 

vo co m O 

O' 

O in 

O 

coo 



o 

•j rt rt 

•i- O 


co -3- hi 

HH 

04 O' 

o 

HH 


% 

cn 

03 

U 

Hi 

04 


HH 


04 

o 

HH 




HH 



■SiR 













O 

Tf 04 

VO CO R Is 

o 

co co 

04 

O' O 


in 

a 


HH 

o 


CO vo Is CO 

04 

in O 

o 

VO Tj- O 



a5 


co O 


CO 04 Hi 

co 

04 fs 

o 

HH 



HH 

tuo 

c 

a 

HH 

CJ 


HH 


co 

o 

rH 



<-> 

W 


\R 











a 


O 

O' o 

vo 04 O' O 

O oo co 

o 

Is c) 

CO 

vl 

O' • 

u 



HH 


■v^-vo hi cor^vo hi 

O' 

oo iop 


S 


04 

O' 


H In HH 

04 

04 Hi 

O' 



# 

o 



HH 

Hi 


HH 



O' 



«o 

HH 



' RR 











C0 K* 

CJ 

O 

O 

HH 

O • co co 

o 

vo O 

04 

M O 


J. d. 

o 

03 

hX u 

>> 3 
<X3 

03 

< 

O 

CJ 

HH 

vO 

m 

cn 

HH 

04 

h- • H Hi 

04 • 04 

CJ 

vO 

vo 

vO co 
co 

04 

HH 

o 

O O 

TT hh 

O' 

HH 

33 






• 



HH 







• 

u 


• • • • 

• • • 

* 




• • 

• • 



• 




43 


* * • . 

' * • . 




• • 

• 



• 


c 

_o 

*ZJ 

CTj 

*-) 

* 5 , 

u 

V 

u 

Pu 


C/5 

c/3 

V 

V 

o 

u 

a. 


a 

o 

u 

aJ 


c; 

4-1 
4-> 

aj 

e 

o 
v- E 

V rt 


:3 

CJ T3 

rt *c -- 

o oj y 
•»—« co 


aJ 

o 


Cj ' 


c 

o 

u 


<L> 

£ 


Cy <-> 

C 43 


(J 

2 u 

3 C 

Oh I—' O • f* 13 *3— *'■ 

») n33 «) r.-n S O 

- O 3 >- g *>•- 3 c 

i G, 


o 

43 




3 £0 ° ^ £ s’-p 3 a 


c 

o 

E 
E 

_ rt 

aJ G o 
jp 43 <-> 

a ■ 

in O ct 
0^3 

J3 cr 
P*Z> W 


c 

o 

♦-> 

4 h 

43 

a, 

(3 

J 3 

rt 

> 

•o 

43 

4-1 

jrt 

*P 

o 

r 1 « 

aJ 

u 



















































































PREVENTION- OF NUISANCE . 


395 


able odor, and a better plan in many cases is to prepare deep 
furrows, run the sludge into these, and cast a heavy earth 
covering over them from other parallel furrows prepared for 
the next batch of sludge. 

Where there is not the land or other facilities for using’ 
sludge-beds (and much land is needed, since each bed, after 
an application of sludge, requires a long rest), the sludge is 
generally pressed into cakes by squeezing out the diluting 
water and reducing the amount of this from about 95$ to 
from 50 <f 0 to 75 ft. The cakes are formed by filter-presses, 
composed of a number of circular or square iron cells (in East 
Orange 36, Columbian Exposition 60, and Worcester 125), 
the faces of which are grooved and recessed, which rest 
vertically face to face in a simple frame and slide away from 
each other on horizontal guides. Between each two cells is a 
canvas bag. Through these cells passes a central feed- 
passage through which the sludge is forced into the canvas- 
lined cells, the water being expelled through the canvas by a 
pressure in the feed-pipe of about 100 pounds per square 
inch. In Worcester the cakes thus formed are 36 inches in 
diameter and ^ inch thick. They give off little odor. They 
will burn without other fuel if containing no more than 70$ 
to 73$ of water. 

The fluid forced out by the press is treated again, either 
combined with the crude sewage or in separate tanks. To 
enable the water to separate more readily from the sludge, 
milk of lime is generally added to this to “ cut the slime.” 

In Worcester one part of sludge is obtained from ninety 
of sewage, there being one ton of solid matter to 750,000 
gallons of sewage, 34^ of this being organic matter. With a 
lime precipitant there will be about .4 lb. of sludge per 
capita daily. This can be burned, used for filling in, or 
buried in pits. The first method is the best, an ordinary 
garbage-cremator being used. It has been suggested that 


SE WEE A GE. 


39 6 

the addition of peroxide of manganese to sludge will supply 
oxygen and prevent putrefactive action; but this has not 
been tried on a practical scale and the expense would prob¬ 
ably be prohibitive. 

Art. 92. Cost of Precipitation. 

The Glasgow plant, to treat 10,000,000 gallons daily, cost 
•$ 335 > 000 exclusive of site. The cost of the treatment is $17 
per million gallons, or 14J cents per capita annually. 
London, to handle 250,000,000 gallons daily, paid $4,066,448 
for a plant, including $662,322 for six sludge-ships. The 
precipitation expenses are $2.98 per 1,000,000 gallons, sludge 
disposal $1.66. The New Rochelle plant, to treat 750,000 
gallons daily, cost about $19,000. The East Orange, for 
1,500,000 gallons daily, cost $75,000; maintenance 60 cents 
per capita annually, exclusive of interest; lime 95 cents per 
barrel, alum ij cents per pound. Round Lake in 1892 paid 
3^ cents per pound for perchloride of iron. The White 
Plains plant, for 400,000 gallons daily, cost $50,049; mainte¬ 
nance $12 per day for 250,000 gallons. At Chautauqua the 
cost of the plant was $16,500; that of chemicals (lime at 83.2 
cents per barrel and alum at 2.15 cents per pound) was, in 
1893, .04 cent per capita per day; total maintenance 57 
cents per capita per year. At the Columbian Exposition 
$8.80 per ton was paid for lime, $13.40 for copperas, and 
$20.40 for alum. Worcester pays about $7.00 per ton for 
lixne, $25 for sulphate of alumina (not used there now). In 
the Powers system of chemical treatment used in the 26th 
Ward, Brooklyn, the total cost is about $35 per 1,000,000 
gallons; capacity 4,500,000 gallons per day; cost of plant 
$204,852.64. The cost of pressing sludge into cakes is about 
50 to 75 cents per ton of cake which is 50$ moisture. 


CHAPTER XVIII. 


DESTRUCTION. 

Art. 93. Mineralization. 

Precipitation removes 50$ to 6 o </ 0 of the organic impuri¬ 
ties of sewage, but leaves most of those in solution practically 
unchanged, besides accumulating an embarrassing amount of 
sludge. The only satisfactory treatment of sewage must 
involve a change of the putrescible matter to stable, innocu¬ 
ous compounds or elements. So far as we know this can be 
attained only by mineralization, i.e., the changing of the 
organic to mineral matter. While this change is described in 
chemical terms, it has been found that no mere mechanical 
mixing of chemicals with the sewage will produce it. It is 
only within the past fifteen years that we have had definite 
knowledge as to the changes which organic matter undergoes 
during mineralization, and their causes; and this subject is 
as yet but incompletely understood. 

Stated briefly, investigation to date seems to prove the 
following as facts : Lifeless organic matter is stable in the ab¬ 
sence of moisture, but in its presence a large proportion of 
such matter is readily broken down in structure and is resolved 
into minerals, appearing generally as mineral compounds. 
Albuminous matter is particularly unstable; while woody 
fibre, bones, and similar matters are quite stable, and cause 
most of the difficulty experienced in sewage purification. 
Organic matter is decomposed not so much by chemical action 
as by certain classes of bacteria, some of which exist in all 

397 


398 


SE WERA GE. 


soils, and probably in water and air as well. Certain of these 
seem to require the presence of free oxygen for their action if 
not for their life, and are called aerobic ; others, the anaerobic, 
live and work best in the absence of light and air; and still 
others are facultative, i.e., can live and act under either con¬ 
dition. 

When sewage enters a sewer it generally contains a small 
amount of free oxygen and a few nitrates. By the action of 
aerobic bacteria the free oxygen is taken up by the urea, am¬ 
monia, and easily decomposable matter present, and nitrates 
are formed. At the same time anaerobic or facultative bac¬ 
teria, together with a few aerobic ones, are at work breaking 
down the albuminous matters into soluble nitrogenous com¬ 
pounds; which operation is carried on with increased activity 
after the disappearance of all free oxygen, the anaerobic bac¬ 
teria being the more effective in liquefying sewage. It is dur¬ 
ing this stage,—in some cases at its beginning, in others when 
it is well advanced,—that the sewage is generally received at 
the purification works or discharged into the river or ocean. 

If it should now be left stagnant, as in a cesspool, the 
anaerobic bacteria would continue the breaking down of the 
organic matters, even the cellulose and fibrous matter being 
finally liquefied. If, however, the sewage be left stagnant for 
too long a time, the bacterial action becomes more or less in¬ 
hibited by enzymes or other products of such action, although 
it will still continue. During this anaerobic action much of 
the organic matter is changed into hydrogen gases (since no 
free oxygen is present), such as marsh-gas, and sulphuretted 
hydrogen, and nitrogen, much of which escapes into the air; 
the sewage meantime becoming offensive to sight and smell. 
In this condition it is called septic sewage. 

If oxygen be admitted to the sewage as soon as it becomes 
well liquefied, but before it reaches this foul condition, oxida¬ 
tion will quickly begin, and the dissolved and finely commi- 


DESTRUCTION. 


399 


nuted organic matter will be changed to innocuous and 
inoffensive nitrates and carbonates. The most offensive septic 
sewage will become oxidized ultimately under favorable con¬ 
ditions, but may create a nuisance meantime. 

Previous to oxidation most of the decomposed nitrogenous 
matter which has not escaped as gas has taken the form of 
ammonia. By oxidation and the action of the aerobic bac¬ 
teria the ammonia becomes changed largely into nitric ot 
nitrous compounds with some base, such as potassium or 
sodium, present in the sewage. Probably none of these 
changes is the effect of only one class of bacteria, but several 
classes work both together and successively. These processes 
are summarized by Dr. Rideal as shown in the following 
table: 



Substances dealt with. 

Characteristic Products. 

Initial. 



Transient aerobic 
changes by the oxygen 
of the water-supply, rap¬ 
idly passing to : 

Urea, ammonia, and 
easily decomposable 
matters. 


First Stage. 



Anaerobic liquefac¬ 

tion and preparation by 
hydrolysis. 

Albuminous matters. 
Cellulose and fibre. 
Fats. 

Soluble nitrogenous 
compounds. Fatty acids. 
Phenol derivatives. 
Gases. Ammonia. 

Second Stage. 



Semi-anaerobic break¬ 
ing down of the inter¬ 
mediate dissolved bod¬ 
ies. 

A m i d o - c ompounds. 
Fatty acids. Dissolved 
residues. Phenolic 

bodies. 

Ammonia. Nitrites. 

Gases, j 

Third Stage. 



Complete aeration ; 
nitrification. 

Ammonia and carbo¬ 
naceous residues. 

Carbonic acid, water, 
and nitrate. 


The process above outlined is, so far as we know, the only 
one other than burning (rapid oxidation) by which organic 
matter can lose its noxious properties. 

It is important to note that liquefaction must precede 











400 


SEWERAGE . 


bacterial nitrification, and that the anaerobes are the most 
effective liquefying agents; also that any attempt to reverse 
these processes will merely retard final purification. 

One of the difficulties of stimulating these processes in the 
purification of sewage is that the various components of this 
resist liquefaction so unequally that it seems impossible to 
make the conditions at all times most favorable to each of the 
contained organic matters. If light and air are excluded to 
encourage the anaerobic action until all the fats and fibres are 
liquefied, the albumens will meantime reach the last stages of 
offensive putrefaction. By making the conditions alternately 
favorable to aerobic and anaerobic action at short intervals, 
each particle of matter may be oxidized as soon as it has be¬ 
come prepared for this action and objectionable odors be 
largely avoided; but under these conditions neither class of 
bacteria will develop and act to the best advantage. 

The bacteria necessary for the above process exist in the 
sewage, but their numbers and the celerity of their action can 
be greatly increased by collecting and retaining them in a 
permanent lodging-place with favorable environment and sup¬ 
plying a constant amount of pabulum in successive doses or 
in a continuous stream of sewage. Most plans for the de¬ 
struction of sewage have for their aim the supplying of these 
conditions. In some but one lodging-place is afforded, and 
either both the liquefying and nitrifying organisms exist and 
act side by side (possibly only aerobic liquefiers acting) or in 
separate parts of the plant, or no liquefaction takes place after 
the sewage enters the plant. Other plants are divided into 
two or three, or even more, separate parts, each devoted to a 
different class of bacteria. In many instances sewage is flowed 
over and settles down through porous soil, in passing through 
the interstices of which it comes into intimate contact with 
the contained air and with the bacteria which adhere to the 
soil particles; and if the passage of the sewage be sufficiently 


DESTRUC, TION. 


401 


slow and the number of nitrifying bacteria sufficiently large, 
the oxidizable liquefied organic matter will all be transformed 
into nitrates. If the number of bacteria is not originally 
sufficient, they will increase with great rapidity; and if a con¬ 
stant amount of sewage be applied continually to a given plot 
of ground, and sufficient oxygen be furnished, the number of 
bacteria will in a few days become sufficient to effect complete 
nitrification. If the sewage be simply turned continuously 
upon this land, the interstitial air will soon yield up all its 
oxygen, and nitrification will cease. But if the land be allowed 
to drain out, the interstices will again fill with air and the 
operation can be repeated ; and this can go on indefinitely, or 
until the filter becomes clogged with unliquefied matter. This 
is the principle upon which purification by land and by filter- 
beds acts. If the land be too open and porous, the sewage 
will pass through too rapidly to permit of thorough bacterial 
action. If it be composed of too fine grains, capillary attrac¬ 
tion will be so great that it will drain out and be reaerated 
but slowly. The time required for draining out a bed is in 
some plants reduced by making the bed very porous and 
holding the sewage in it during fixed periods of time by clos¬ 
ing the outlet. In other cases the beds are not drained out 
at all, but air is continuously forced in under a few ounces 
pressure. These methods, depending upon the aerobic bac¬ 
teria only, must use sewage in which are no matters in sus¬ 
pension not easily liquefied by aerobes, or else be subject to 
clogging, the fine-grain filters mainly upon the surface, the 
coarse-grain ones in all their interstices. For this reason some 
preliminary process for removing or liquefying the suspended 
matter must generally be provided. Chemical precipitation 
has been adopted in many plants as a preliminary to filtration 
or land treatment; and many of those which have not adopted 
this retain the sewage for a short time in sedimentation-tanks. 
The disposal of the sludge thus deposited is a most trouble- 


402 


SEWERAGE. 


some question, and various plans have been tried for avoiding 
the formation of this. In the “ bacteria-bed ” of Dibdin very 
porous material is used—■£ to 2 inches diameter—which will 
drain out thoroughly and quickly, and will permit the coarse 
suspended matter to enter the whole body of the filter, and 
not the surface only. This material is placed in a tank or pit 
in which the sewage is retained for about two hours, permit¬ 
ting the bacteria to act during that time, the organic matter 
being practically all liquefied and a large part of it nitrified. 
The effluent can then be filtered through a fine-sand filter 
many times as fast as could crude sewage, with equally good 
results. The name “contact filter,” which has been applied 
to these beds, seems more appropriate than that originally 
used, since all filtration methods depend upon bacteria for 
their action. The theory of action of these filters is as 
follows: “When the effluent flows from a filter, air is drawn 
into the filter again and fills the open space. Consequently 
a partial oxidation of the organic matter left within the filter¬ 
ing material proceeds until this oxygen is exhausted, when 
the open space is completely filled with the chief products of 
this oxidation,—namely, carbonic-acid gas, marsh-gas, nitrogen 
of the air primarily present and nitrogen liberated during 
decomposition,—and the filter will remain with its open space 
filled with these gases until they are removed by the intro¬ 
duction of sewage or air. This condition reached, the activ¬ 
ity of the oxidizing and nitrifying bacteria within the filter 
ceases and anaerobic actions begin, which change a consider¬ 
able portion of the organic matter adhering to the filtering 
material into forms easily soluble and oxidized by the air 
introduced when the filter is again flooded.” (Mass. State 
Board of Health, 1899.) If these filters are used in pairs, the 
effluent from the ‘ ‘ first-contact filter ” passing to the ‘ ‘ second- 
contact filter,” the action in the former becomes almost wholly 


DESTRUCTION. 


403 


anaerobic, that in the latter aerobic; and a high degree of 
purification may be attained. 

In the Scott-Moncrieff “cultivation filter” the sewage 
passes upward through flints or other stones, leaving the solid 
matter behind, but carries with it all matter liquefied from 
sludge previously deposited. Here the aim is to combine 
both liquefaction and nitrification in the same filter, the lique¬ 
fying anaerobes being segregated in the lower part, the nitri¬ 
fying bacteria in the upper; although the former class of 
bacteria sometimes occupy the entire filter. 

Another attempt at solving the sludge problem is the 
“septic tank,” originally a dark, air-tight tank of such size 
that each particle of sewage would occupy twenty-four hours 
in passing through it. (Recently successful ones have been 
made neither dark nor air-tight.) During this time anaerobic, 
putrefactive bacteria break down the suspended organic mat¬ 
ter, and sedimentation carries to the bottom most of the sus¬ 
pended inorganic matter and some of the organic; a part of 
the organic matter floating in a thick zooglaea scum on the 
surface. The organic matter leaves the tank in a greater or 
less time, 25 % to 35^ escaping as carbonic acid, free nitrogen, 
and marsh-gas, and most of the remainder passing off in the 
effluent in solution or in a finely divided state; a small part 
only remaining permanently in the tank as ash. 

Each of these methods has been advanced by some enthu¬ 
siasts as a substitute for nitrification ; but they really should 
be compared rather with chemical precipitation, since the 
effluents from them should not be discharged directly into 
rivers except when the dilution afforded is considerable and 
avoiding a nuisance is the only aim. 

In all methods requiring the action of bacteria several days 
must elapse after the first sewage is applied before there will 
be present a number of bacteria sufficient for the greatest 
efficiency. Since one bacterium may in twenty-four hours 


404 


SEWERAGE. 


multiply into millions, the production of a supply to meet a 
given demand is quite rapid. But a sudden increase in rate 
of application of the sewage may overtax the bacteria present 
and result in decreased efficiency. 

It has been found that not only is the organic matter re¬ 
moved from sewage by the various methods of purification, but 
the bacteria also are thus reduced in number: by more than 
99$ by passing it through suitable fine-grain filters, and to a 
less degree by the other methods. The finer the sand of a 
filter the less the number of bacteria in the effluent; but 
those removed can hardly have been strained out by the 
sand, owing to their small size; and it is supposed that a 
large number are removed by a film of gelatinous substance 
which forms upon the surface of the filter,* and that by nitri¬ 
fication the conditions in the effluent are rendered unfavorable 
to the life of the remainder. By some methods of purification 
the bacteria are thought to be killed outright. 

The different methods and natural processes commonly 
employed have been briefly outlined above, and will be con¬ 
sidered more in detail in the following articles. 

In the majority of cases the effluent from a disposal plant 
is discharged into a stream, and it becomes an important ques¬ 
tion how great a purification is necessary to prevent the creat¬ 
ing of a nuisance. It should be realized that the conditions 
in no two cases are exactly the same, and that the amount of 
purification required will depend upon the original pollution 
and relative quantity of the sewage and the stream, since the 
mixture of stream and effluent must be of such a character as 
to purify itself readily. It should be (but seldom is) required 
that the organic matter discharged be in such quantity and 
condition that it may be entirely oxidized before the stream 
bearing it reaches the next city. The processes of self-puri¬ 
fication of streams have been already referred to (page 24). 


DESTRUCTION. 


405 


The matter settling to the bottom is worked over by bacteria 
in the same way as is the sediment in a septic tank, but all 
the gases as well as the liquefied organic matter are oxidized 
by the stream, except where the pollution is excessive and the 
stream sluggish. It frequently happens that while this matter 
is still but partly oxidized the stream receives organic matter 
from another city or other source, when not only is the fresh 
organic matter not completely oxidized, but the nitrates 
already formed are compelled to yield up a part of their 
oxygen. This effect, and the later oxidation, are shown by 
chemical analyses taken in the Scioto River at Columbus, O., 
December 4, 1897: 


• 

Distance, 

Miles. 

Color. 

T urbidity. 

Sediment. 

Odor. 

Oxygen 

Required. 

Sandusky Street Bridge.. 

O 

0.6 

Marked 

Distinct 

Slightly earthy 

O.91 

Frank RoaH Rriri^e. 

A 

0.4 

i « 

Marked 

Oily 

I.05 


I 


Sh a d p vil 1e Bridge. 

II 

0.4 

( < 

Distinct 

Musty 

O.91 





Ammonia. 

Nitrogen as 

Chlorine. 

Hardness. 

Total Solids. 

Free. 

Albuminoid. 

Nitrates. 

Nitrites. 

Temporary. 

Permanent. 

Sandusky Street Bridge.. 

.OIIO 

.0418 

.582 

.0025 

O.23 

14.4 

13.6 

47-4 

Frank Road Bridge. 

.0880 

.0780 

.442 

.0070 

O.60 

16.O 

13-4 

47.2 

Shadeville Bridge. 

.0508 

.0536 

•536 

.0037 

0-53 

15-2 

ii. 6 

43-8 


Here it is seen, by the presence of nitrites and ammonia, that 
organic matter not completely oxidized existed in the stream at 
Sandusky Street Bridge; that at Frank Road Bridge, just 
below the sewer outlet, much of the nitrate has changed to 













































406 


SE WEE A GE. 


nitrite, the oxygen yielded forming nitrites of the fresh organic 
matter; and that at Shadeville, 7 miles below, much of the 
ammonia and nitrites has changed to nitrates. The addition 
of sewage at Frank Road is indicated by the increase of 
chlorine, the oxygen consumed, ammonia, and nitrites also 
showing an increase in organic matter. 

It is evident that to prevent occasioning a nuisance by 
pollution of the stream, the organic matter added should be 
in a form readily oxidized, and the amount of “ oxygen con¬ 
sumed ” by the entire amount of effluent should be no greater 
than can be furnished by the stream, or by that part of it 
with which the effluent becomes intermingled before the next 
addition of pollution. (The amount of dissolved oxygen in 
well aerated river water is approximately one part per 100,000 
of the water, by weight.) Oxidation in a stream is probably 
not so rapid as in a filter, because the oxidizing bacteria are 
not so numerous; being only those which exist in the stream 
and effluent, since there exists in the stream no fixed lodging- 
place in which they may multiply and act upon successive 
particles of matter. Since the quantity of water flowing in 
the stream determines the amount of pollution permissible, 
and since this varies, it follows that a degree of purification 
which is satisfactory at one time would cause a nuisance at 
another; therefore, that a less degree of purification is per¬ 
missible during high water than during low. 

The above applies to preventing a nuisance. But with the 
oxidation of all organic matter the water would become safely 
potable were it not for the possible presence of pathogenic 
bacteria. There is much uncertainty as to the probable 
length of time these may exist in flowing water. That the 
total number of bacteria is diminished is illustrated by the 
following analyses of the Desplaines River, which receives 
Chicago’s sewage. (By Prof. E. O. Jordan in 1900.) 


DESTRUCTION . 


407 


Sample taken at 

Distance 
from Morris. 

Number of Colonies per Cubic Centimeter. 

Right Bank. 

Centre. 

Left Bank. 

Morri«;. 


261,000 

204,000 

29,000 


^ 12 miles ) 

Seneca . 

1 24 hours f 

100,000 

49,000 

35,000 

Ottawa. 

\ 24 miles ) 

} 48 hours f 

11,500 

10,700 

13.500 


This shows a mean decrease of almost 93$ in the number of 
bacteria in 24 miles; probably largely due to sedimentation, 
which is encouraged by the sluggish flow. The table also 
illustrates the slow intermingling of sewage and stream under 
such conditions. With a rapid current the intermingling 
would be more thorough, but the stream might flow many 
times this distance before losing the same number of bacteria. 
What percentage of the bacteria remaining are pathogenic is 
not known ; but there seem to be good reasons for supposing 
that the percentage of these removed is greater than of the 
non-pathogenici (See also page 27.) 

Art. 94 . Broad Irrigation. 

“ Broad irrigation means the distribution of sewage over 
a large surface of ordinary agricultural ground, having in view 
a maximum growth of vegetation (consistently with due 
purification) for the amount of sewage supplied. Filtration 
means the concentration of sewage at short intervals, on an 
area of specially chosen porous ground, as small as will absorb 
and clean it, not excluding vegetation, but making the produce 
of secondary importance.” (Royal Commissioners on Metro¬ 
politan Sewage Discharge.) No more definite line could be 
drawn between irrigation and filtration than is indicated by 
these definitions. In many plants the same land is used 
alternately for both methods. The nitrates which would pass 
off with the effluent in filtration are to a certain extent (10$ 
to 20 io probably) absorbed by vegetation. 


















408 


SE WERA GE. 


In broad irrigation much of the sewage must at times be 
diverted from the crops—as in rainy weather or after the 
fruit has matured. If this is not done, the crops cannot be 
raised to advantage. In some locations it will not be seri¬ 
ously objectionable to turn the sewage at these times into the 
streams, particularly in rainy weather when these will be in 
flood; but where this is not permissible provision must be 
made to treat the sewage otherwise, as on filtration-beds. 
If this plan is adopted sewage should be turned upon the 
filtration-beds two or three times a week to keep alive in 
them the nitrifying bacteria. 

Irrigation-fields are ordinarily odorless, but on close, 
humid days in summer the moist deposit on the surface gives 
off an appreciable dish-water smell, which, however, is seldom 
noticeable more than ioo yards from the field. The intensity 
of the odor seems to increase not directly with but as the 
square or some higher power of the area irrigated. It is not 
advisable to place such grounds in the midst of a settled 
community, but a quarter of a mile should be sufficient inter¬ 
vening space. 

Sewage is used in irrigation much as water is, except that 
it should not come into direct contact with berries, celery, 
cabbage, or the edible portions of any plant. In some cases, 
generally where grass of some kind is grown, the sewage flows 
slowly all over the land in a thin layer. Where corn or 
vegetables are grown they are usually planted on the narrow 
ridges between ploughed furrows into which the sewage flows, 
and where it stands, soaking downward and sideways into the 
soil. The roots of vegetation and the vegetable mould which 
forms on the surface of the ground prevent the rapid absorp¬ 
tion of the sewage, and unless the subsurface soil be clayey 
or quite non-porous, sub-drains are not often necessary, but 
ditches are carried through the farm at intervals to receive 
the drainage. If the sewage is not clarified before being 


DESTRUCTION. 


409 


applied to the soil, an impervious skin shortly forms, composed 
of filaments of paper, rags, and similar matters, together with 
grease and the more stable organic matter; and this must be 
frequently removed if the ground is to be re-aerated and kept 
absorptive. This matter, which has little odor, can be piled 
in a dry spot and burned occasionally. 

If the ground is not level, the furrows should follow con¬ 
tours, that the sewage may stand in them. If, on a sloping 
land, furrows are not desired, the catchment system may be 
employed. In this a series of ridges following the contours 
are placed at intervals of 15 to 100 feet down the slope; the 
sewage is held behind each ridge until it overflows it, when 
the surplus runs over the surface until intercepted by the 
next ridge. The object of the ridges is to prevent the sewage 
from gathering into channels and attaining erosive velocity. 
Hence the steeper the land the closer should be the ridges to 
each other. This method was adopted at Wayne, Pa., on a 
steep rocky hill 100 feet high with a soil of micaceous loam. 

The ridge-and-furrow system is particularly applicable to 
revel land. In this system the ground is divided into beds 
sloping from a central ridge to gutters or furrows on each side, 
each furrow being common to two adjacent beds. Another 
furrow for distributing the sewage runs along each ridge, from 
each side of which the sewage overflows in a thin sheet. The 
beds are generally 15 to 20 feet from each ridge to either 
furrow, and of any convenient length. The slope of the beds 
is a matter of judgment, being steeper the more porous the 
soil in order that the sewage may be evenly distributed. 

Sewage is in some cases distributed through main carriers 
of iron or of vitrified pipes, under pressure produced either 
by gravity or by pump, to hydrants, as at Pulman, Ill.; 
through vitrified pipes by gravity, as at Summit, N. J.; or 
through open channels, lined with concrete or with split pipe; 


4io 


SE WEE A GE. 


and in many recent works the channels are used without any 
lining whatever. From the main carriers the sewage is 
diverted by means of simple gates to secondary carriers, which 
are often but ploughed furrows, the location of • which is 
changed when they become clogged with sewage. These 
furrows should be closer together the more pervious the soil, 
to effect uniform distribution. If the subsoil is clayey, or 
the water-table is near the surface, it may be necessary to lay 
sub-drains. These are generally placed under the ridges if 
the ridge-and-furrow method is used. From 3 to 6 feet is 
the customary depth, depending upon the porosity of the soil 
and the crops grown. Sub-drains cannot be used near osiers, 
since these root deep and stop up the drains. 

Open, porous soils are best adapted to irrigation ; although 
they should not absorb the sewage faster than 25,000 to 
30,000 gallons per acre per day to obtain good results from 
crops. But if the crops are only an incident (“ intermittent 
filtration ”), the more porous the soil the better. Clay land 
may be improved for irrigation by ploughing-under ashes or 
sand, but can never be made as desirable as naturally poious 
soil. The sewage from 50 to 150 or 200 persons can be used 
for irrigating one acre, depending upon the quality of the 
soil. At the Paris sewage farm at Acheres 11,766 gallons 
per acre daily is fixed as the limit, but this is largely street- 
water. At Berlin the population contributing to each acre 
of the irrigation-fields is 156. 

Art. 95 . Crops. 

Crops of all kinds have been grown on sewage farms. 
Italian rye-grass seems particularly well adapted to this 
purpose, absorbing sewage indefinitely and growing so closely 
as to choke out weeds, but is not very hardy in this country 
north of Washington, D. C. It is grown in fiat beds. It 








DESTRUCTION. 


4 1 ? 

makes excellent fodder and is a good crop for dairy farms,* 
but when cut can be kept only by ensilage. It is sown at the 
rate of 45 to 50 pounds per acre. 

In the northern United States corn has given excellent 
satisfaction. At South Framingham, Mass., 100 bushels of 
shelled corn per a\me has been grown; at Brocton, Mass., 70 
bushels is obtained. The corn is grown in hills 3 feet apart, 
the ridges being about 4 feet apart, and is irrigated through 
the furrows. 

Wheat has been grown at the Salt Lake City farm, 36 
bushels per acre, and barley 28 bushels per acre; but cereals 
are apt to develop stalk rather than grain on sewage farms. 
Walnuts give good results in Pasadena, Cal. Cabbages, 
parsnips, carrots, potatoes, rhubarb, turnips, cauliflower, 
celery, onions, squashes, beans, peas, asparagus, as well as 
other garden truck, and tobacco, have all been grown on sew¬ 
age farms, as have timothy, alfalfa, and other grasses. Only 
actual trial in a given section of country will determine the 
crop which there grows best and finds the best market. 

Meadow-land at Paris (Gennevilliers) is uninjured by a 
flow of 50,000 gallons per acre per day. Lucerne grass takes 
36,000 gallons ; artichokes 12,000 gallons ; flowers and 
parsley 11,000; leeks, cabbage, and celery 7000; beets, 
carrots, and beans 4000; potatoes, asparagus, and peas 3000 
gallons per acre per day. 


* Dairy products arc considered by many English cities the most profit¬ 
able yet tried; Birmingham selling $20,000 to $30,000 worth of milk an¬ 
nually from its sewage farm. 



412 


SE tVEXA GE. 


Art. 96 . Filtration. 

A city of 100,000 inhabitants, if treating its sewage by 
irrigation, would require 500 to 2000 acres of suitable land. 
This is not always obtainable, or only at great cost; and for 
this reason it might be better to adopt filtration, which 
requires less area. Filtration may be effected through 
natural soil, if this is fairly porous, or through specially pre¬ 
pared beds of sand, gravel, coke, or other substances. 

Where natural soil is used care is taken to keep this open 
and free on top, so far as possible; and the sewage is turned 
•onto it at regular intervals and in given quantities, regardless 
of the requirements of any vegetation thereon. The beds 
are ploughed into ridges and furrows, or are surrounded by 
high banks and flooded to the depth of several inches or even 
feet. At Berlin the filtration area is made into furrows 18 
inches deep by 2 feet 6 inches wide, separated by ridges 3 
feet wide. Crops may or may not be grown on the ridges. 
At Brocton, Mass., cropping has not been found advisable 
for clarified sewage; but corn is grown to advantage in beds 
upon which the sludge from the settling-tanks is placed. 

If the soil is dense, the sewage may be flooded onto beds 
surrounded by banks. But otherwise the use of furrows is 
preferred for insuring general distribution of the sewage. If 
the soil is very porous, there is a tendency for all the sewage 
to enter it near the carrier-outlets. Under such a condition 
numerous secondary carriers may be used, composed of boards 
formed into shallow V-shaped troughs. Uniform distribution 
may also be assisted by giving considerable slope to the 
surface of the beds. In both filtration and irrigation great 
care must be used to prevent the formation of puddles in 
which the sewage will stand and putrefy. The surface of the 
ground in the furrows will shortly become clogged with 
organic matter, which resists immediate decomposition, but 
would be broken down and oxidized if given time. Furrows 


DESTRUCTION. 


413 


should then be opened in the ridges where the soil is probably 
unclogged, the earth being thrown into the old furrows. In 
time a considerable amount of undecomposed organic matter 
will collect throughout the interstices of the filter, and this 
should then be given a rest for several days or week?, for which 
purpose the filtration area should be divided into three or 
more beds, one of which is always resting. Those in use 
should be allowed to drain out after each dose, that they may 
be re-aerated; the sewage generally flowing onto drained beds 
while the ones previously used are draining. In some small 
plants, however, the sewage is received in settling-tanks and 
the effluent discharged upon all the beds at intervals of 
several hours, or even only once a day. 

Filtration areas are usually underdrained; but if the soil 
is porous for a considerable depth and the water-table is low, 
this is not necessary. At the Meriden, Conn., treatment- 
grounds sub-drains were provided, but receive none of the 
effluent, which emerges from the river-bank 11 to 20 feet 
below the outlets of the drains. Sub-drains are generally of 
3- to 6-inch sewer-pipe, laid from 3 to 7 feet deep. 

The efficiency of filtration-grounds in practical use is 
shown by the following analyses: 

ANALYSIS OF SEWAGE, SEWAGE EFFLUENT, AND UNPOLLUTED 


GROUND-WATER FROM SEWAGE-FIELD AT SOUTH FRAMINGHAM, 
MASS. 



Color. 

Total Resi¬ 
due from 
Evapora¬ 
tion. 

Ammonia. 

Chlorine. 

Nitrogen as 

Free. 

Albu¬ 

minoid. 

Nitrates 

Nitrites. 


0.70 

28.30 

1 • 7893 

•3750 

4.07 

.0080 

. OOOI 

“ effluent at underdrains.* 

0.00 

19.45 

0.0335 

.0039 

2.56 

.6018 

.0006 

“ “ “ spring *. 

0.00 

7* 2 3 

0.0000 

.0029 

1.77 

.2350 

.OOOO 

Unpolluted ground-water. 

0.00 

4.70 

0.0000 

.0008 

0.20 

.0083 

.OOOO 


* Little effluent comes from the underdrains. Most reaches a neighboring brook through 
springs. The effluent at the sub-drain is apparently about 35# ground-water, and at the spring 
about 65*. 


At Brocton, Mass., where the sewage is clarified in a 
settling-basin and then distributed to filtration-beds, the fol¬ 
lowing were found to be the average analyses of the sewage 



























414 


SE WEE A GE. 


before and after clarification, of the sludge from the basin,, 
and of the effluent: 



Ammonia. 

Chlorine. 

Oxygen 

Consumed. 

Free. 

Albuminoid. 

Raw sewage. 

2.5722 

O.8964 

6-34 

5 - 8 r 

Clarified sewage. 

2.3636 

O.5728 

6.29 

3-67 

Sludge. 

4-4133 

3-7578 

6.82 

24.69 

Effluent.. 

O.09H 

O.OIO5 

4.80 

0.11 


At Gardner, Mass., in 1893, one acre of bed was provided 
for each 2100 citizens contributing sewage. Two settling- 
basins 7 X 20 feet were used. At Oberlin, Ohio, about 800 
people, and at Central Falls, R. I., 1100, contribute sewage 
to each acre of filtration ground. At Plainfield, N. J., 
37,000 gallons, and at Pawtucket, R. I., 40,000 gallons of 
sewage per acre per day is set as a limit. At the latter place 
89$ to 99$ of the albuminoid ammonia is removed. 

If it is desired to still further economize space, artificial 
filters are constructed. These are generally of sand, of an 
“ effective size ” * of about .01 inch, over coarse sand or fine 
gravel, which in turn rests upon a layer of medium-sized 
gravel, at the bottom of which the drains are placed. The 
greater part of the purification appears to be done in the 
upper layer, since 1,118,000 bacteria have been found per 
gram of sand in the upper inch, while at 4 inches depth 
but 125,000 were found.f The purpose of the finer top layer 


* The effective size of a material “ is such that io per cent of the mate¬ 
rial is of smaller grains and 90 per cent is of larger grains than the size 
given. The results obtained at Lawrence indicate that the finer 10 per 
cent have as much influence upon the action of a material in filtration as 
the coarser 90 per cent.” (24th Annual Report State Board of Health of 
Mass.) 

f It is probable that a large percentage of the great number of bacteria 
found in the upper inch are those strained out of the sewage, only a few of 
which are nitrifying. 




















DESTRUCTION . 


415 


is to regulate the velocity of flow, to insure a more minute 
subdivision of the water and thorough oxidation, and to 
support the gelatinous top coating which materially assists in 
the purification. Care must be used to insure that in no 
place does the sewage pass from a coarse to a fine sand, since 
organic matter would be deposited here and clog the filter. 
By having the finest sand on top all clogging is at the surface 
where it can be reached. For example, the Pawtucket filters 
are raked for 1 inch in depth after every fifth dose, and are 
thus kept free. At Woonsocket, R. I., in 1899, 2 acres of 
filter-beds were constructed having 18 inches of gravel, on 
which was placed 28 inches of coarse sand, and on this 14 
inches of medium sand. At Gardner, Mass., 16 beds con¬ 
taining 82,330 square feet were constructed by placing 4 to 5 
feet of gravel and coarse sand on a clay bottom. 

By intermittent filtration through clean, coarse sand 
50,000 to 100,000 gallons per day of American sewage can 
be treated on one acre, and gyfo to 99$ of the organic matter 
therein removed. With fine sand or sedimentary deposit the 
same result can be obtained with 30,000 gallons or less per 
day if care is taken to allow thorough drainage between 
doses. 

The amount of oxygen introduced by each aeration of the 
bed can nitrify only a given amount of sewage, and if more be 
applied before re-aeration an unsatisfactory effluent must re¬ 
sult. For example, to nitrify five parts of nitrogen per 
100,000 requires a volume of air one-half as great as that of 
the sewage treated. 

Nitrification is favored by certain constituents of soil, such 
as carbonate of lime, and impeded by others. 

Polarite (magnetic oxide of iron 54$, silica 25^, lime, 
alum, magnesia, carbonaceous matter and moisture 21#) is a 
(patented) granular substance used for filtration, but there 
seems to be little evidence that it is more efficient than sand 


416 


SE WEE A GE. 


of a similar size of grain, or finely broken coke-breeze. 
Polarite is generally placed in a thin~layer between an upper 
and a lower bed of sand. 

On the care of filtration areas or beds Mr. Geo. W. Fuller 
has given, in the Report of the Massachusetts State Board of 
Health for 1893, the following suggestions. 

** (1) Systematic raking, with occasional harrowing or 
ploughing, is very satisfactory, particularly for coarse ma¬ 
terials. 

“ (2) Systematic scraping ( removal of clogged material ) at 
regular intervals (followed by raking to loosen the material) 
gives very good results, especially for fine materials. 

“ (3) Systematic scraping when necessary, without raking 
or harrowing, is not advisable. 

“ (4) The efficiency of very fine material (clogged or not 
clogged) is much increased by trenching with coarse material. 

(Digging trenches through the bed and filling them with other 
material, generally coarse sand.) 

“ (5) Such trenches should contain carefully graded ma¬ 
terials at the bottom to prevent clogging at the junction of 
the coarse and fine sand. 

“ (6) When new material is put onto old to replace 
clogged material removed by scraping, it is always advisable 
to mix the old and the new together in order to prevent 
clogging at the junction of layers of unlike capillary attrac¬ 
tion. 

“ (7) The removal of stored organic matter by resting for 
a limited period is sufficiently great to render this simple and 
inexpensive method worthy of careful consideration in cases 
of clogging where the available area is not too limited. 

“ (8) It is important that the treatment of filters be such 
that the condition of operation be as favorable as possible 
during the cold winter weather. 

“ (9) Great care should be taken, especially in the case of 


DESTRUCTION. 


4*7 


filters of fine material, that the capacity of the filter be not 
taxed during the winter months to such an extent that more 
organic matter is stored throughout the sand than can be 
removed during the spring and early summer, which is the 
period of highest nitrification.” 

” Qualitative deterioration is a serious matter in winter, 
because when a period of biological reconstruction is neces¬ 
sary, nitrification cannot be promptly re-established, as is the 
case in summer, but requires a period of several weeks and 
possibly months.” (Report Massachusetts State Board of 
Health, 1894.) 

With reference to the effect of cold and snow upon irriga¬ 
tion or filtration beds, it is found that if snow falls before the 
ground is frozen, there is generally little trouble; but if the 
ground becomes frozen, the sewage usually freezes also if 
flowed over a flat surface in a thin stream. If, however, the 
land be deeply furrowed, there is little danger of the sewage 
freezing. If the land is only slightly porous, flooding to a 
depth of a foot or two will give satisfactory results. The 
sewage should be kept as warm as possible before discharging 
onto beds. There is little bacterial action when the tempera¬ 
ture of the sewage is below 40°; the temperature most favor¬ 
able for rapid oxidation appearing to be 90°; at about 130° 
it entirely ceases. 

Worms and burrowing animals occasionally give trouble 
by opening passages in the soil by which unpurified sewage 
reaches the drains. These have been driven out by flooding 
the land once or twice with very strong or septic sewage. 

The sludge from the settling-tanks is generally pumped 
or flowed upon beds set apart for this purpose, which are 
raked off after each application has dried, and the deposit is 
left piled upon the surface to be burned. In a few plants the 
sludge is taken by farmers for fertilizer. 


418 


SEWERAGE. 


Art. 97 . Cost of Irrigation and Filtration. 

The cost of land for irrigation or filtration plants will of 
course vary with every city. To a certain extent the cost 
of preparing the plant also will vary, depending upon the 
character of the soil and the nature of its surface. A general 
idea of the cost of filtration plants, however, can be obtained 
from the following figures: 

At Spencer, Mass., II acres of partly wooded land was 
prepared, underdrains being placed 5J feet deep. Four- and 
five-inch underdrains cost 11 cents per foot; grubbing, $50 per 
acre; excavation, 15 cents per cubic yard; ploughing and 
harrowing, $6 per acre. Entire cost, $8300. 

At Marlborough, Mass., 20 filter-beds, settling-tank, and 
house cost $2 1,720. 

At Gardner, Mass., 1.9 acres, in 16 beds, of gravel 
brought from neighboring banks, with two settling-tanks each 
7 X 20 feet, used by 4000 people in 1893, cost $10,046. 

At Brocton, Mass., 30 acres in 23 beds, disposing of 
1,000,000 gallons of sewage daily in 1898, and a receiving- 
reservoir 42 X 118 feet, cost about $209,000. Capacity 
2,000,000 gallons daily. 

At Bristol, Conn., preparing 6 acres of filter-beds cost 

% * 

about $9000. 

At Paris, Tex., preparing acres, with 20,179 feet °f 
drains 4 feet deep, and two settling-basins, cost $3730. 

At Pawtucket, R. I., the plant, comprising 2.4 acres, cost 
about $12,000. 

At Medfield, Mass., where no sub-drains are used, land 
for disposing of 25,000 gallons daily was prepared for about 
$1000. 

At Plainfield, N. J., grading 16 acres, sub-drains 5 to 7 
feet deep, settling-basin and pump, cost $31,212. 


DESTRUCTION. 


419 


At Flemington, N. J., preparing 5^ acres for broad irri¬ 
gation cost $5875. 

In general it will cost about $175 to $450 per acre to pre¬ 
pare ridge-and-furrow fields for irrigation, and $15 to $50 to 
prepare fields for the catchment method. 

The operating expenses at Oberlin, Ohio, (5.25 acres,) 
were $460 in 1897, or 17.7 cents per capita. 

At Brocton, Mass., the operating expenses in 1899 were 
$2494, of which $2032 was for the filters proper ($17.67 being 
for handling snow), and the remainder for general care of the 
grounds and miscellaneous expenses. 

At Meriden, Conn., it cost $8.50 per 1,000,000 gallons to 
care for the filtration and irrigation beds in 1896. 

At Plainfield, N. J., the cost of operating 15 acres in 
1898 was $1400. 

On the Berlin sewage farm the labor averages one man for 
each 77 acres, there being in all about 15,000 acres under 
irrigation. 

In England the force per acre required to look after irriga¬ 
tion farms is one man for each 6 to 26 acres; averaging about 
one to each 10 acres. 

Art. 98 . Contact Filters and Septic Tanks. 

A statement of the principles of operation of contact filters 
and septic tanks has already been given on pages 402 and 403 
The practical construction and operation of them has been so 
limited as to both the number and the size of plants that they 
may be said to be as yet largely experimental. In fact, the 
most valuable information which we have concerning these 
has been obtained from experimental plants; notably those at 
Lawrence, Mass., and Manchester, Eng. The Manchester 
experts state : “We would emphasize that our experiments 
clearly show that the key to efficiency in the bacterial treat- 


( 


420 


SE WEEA GE. 


ment of sewage is multiple as opposed to single contact”; 
and the Massachusetts experiments, together with others, 
seem to point to the same conclusion; which is perhaps the 
most important fact demonstrated by recent investigations. 
Heretofore attention has been paid almost exclusively to 
aerobic nitrification ; but the importance of anaerobic lique¬ 
faction is now appreciated. It still remains true, however, 
that the aerobic action is the more important. 

If we consider the process of purification divided into two 
parts, the former is provided for by the first-contact filter or 
the septic tank; the latter by the second-contact filter or the 
fine-grain filter. The Moncrieff cultivation filter is essentially 
a continuous-flow first-contact filter in which the sewage enters 
from below instead of from above. A third fine-grain filter is 
sometimes used; and Moncrieff has employed six or seven 
filters, one above the other, for purifying the effluent from his 
cultivation filter. 

A first-contact filter consists of a pit generally about 3 feet 
to 8 feet deep; although at the London purification plant one 
13 feet deep operates successfully. The pits have generally 
been made water-tight, but this does not seem to be essential; 
and experimental ones at Manchester were simply excavated 
from the soil, with side slopes of 2 to 1. On the bottom of 
the pit is laid a series of drains leading to a main outlet-pipe, 
which is provided with a valve for regulating the flow of sew¬ 
age from the filter. The pit is then filled with coke, coal, 
slag, cinders, gravel, burnt clay, glass, or other clean, insoluble 
material of fairly uniform size. Coke breeze gives excellent 
results, although it is liable to slow disintegration. The 
Manchester experts obtained their best results from clinkers 
passing through ij-in. mesh and rejected by J-in. ; and this 
material is recommended by the Massachusetts Board of 
Health. Both of these bodies of investigators found that the 
contact beds had at first a water capacity of about 50#, but 


DESTRUCTION. 


421 


that this was quickly reduced to about 33$, at which it re¬ 
mained constant; the reduction being due partly to the 
growth of bacterial jelly on the surfaces of the filter material, 
partly to chaff, straw, and wood and cloth fibres. To prevent 
the filling of the filter by sand or other solid mineral matter 
a pit or catch-basin should be placed above the filter, through 
which the sewage should flow at such velocity as to carry on 
all but heavy insoluble matter. Such a catch-basin should be 
provided for septic tanks also, as well as for all kinds of filters. 

As already stated, the operation* of a contact filter consists 
in filling the filter, allowing it to remain full for a fixed time, 
emptying, and allowing it to stand empty; two hours being 
allowed for each operation in many cases. It was found at 
Lawrence that if the sewage stood but two hours in a single¬ 
contact bed which was filled once daily, the action during this 
time was aerobic only, the anaerobic action taking place while 
the tank stood empty. The rests between doses should not 
be long enough to permit the bacteria to die from lack of 
pabulum, but these should be preserved in the filter to work 
over successive doses. For this reason also the sewage should 
not be allowed to enter or leave the bed with so great velocity 
as to wash the bacteria out of the filter. 

Instead of filling the filter-beds at intervals, it is main¬ 
tained by some that the flow through them should be contin¬ 
uous; their argument being that by this method constant 
conditions are maintained, while by intermittent filling the 
conditions in each filter alternately favor the aerobic and 
anaerobic bacteria, interfering with the greatest activity of 
either. 

When the sewage is introduced at the top of the filter it is 
distributed through troughs reaching all parts of the surface; 
or the surface is covered with a thin layer of coarse material 
to prevent washing, and the sewage is flooded on from one or 
more points; or it is in some cases distributed by revolving 


* See Appendix III. 




422 


SE WEE A GE. 


arms which cause it to fall in spray or drops on all parts of 
the surface. The last method is probably the most efficient, 
but is difficult of application to large plants, and it is thought 
that no sprinkling arrangement has yet been devised which 
will not clog with the suspended matter in the sewage. 

If a contact bed is filled three times a day, and its inter¬ 
stices have a volume one-third that of the entire filter, it is 
evident that the daily capacity of the filter is its cubical con¬ 
tents. A filter 5 feet deep could therefore treat 37 gallons 
per sq. ft. per day. Allowing for walls or embankments be¬ 
tween filters and occasional resting or cleaning of beds, it is 
thought that 25 gals, per sq. ft. per day, or say 1,000,000 
gals, per acre, can be purified. If double contact is em¬ 
ployed, as it should generally be, double the area will be 
required; or 500,000 gals, per acre per day can be rendered 
unputrescible; which was the* conclusion reached by the 
Manchester Commission. It was concluded from experiments 
at Leeds on continuous-flow contact filters that by passing 
through them this same amount per acre of effluent from 
septic tanks over 90$ purification can be obtained—more than 
is necessary to avoid putrefaction. Double-contact filters, 6 
feet deep, in London have removed practically all the sus¬ 
pended matter and 51$ of the dissolved putrescible organic 
matter, when receiving 600,000 gals, of crude sewage per acre 
per day. Dibdin in 1895 filtered through 3 feet of coke 
breeze the effluent from a lime-precipitation plant at the rate 
of 1,000,000 gals, per acre per day, the effluent from the con¬ 
tact filter containing 71# less albuminoid ammonia and ab¬ 
sorbing 77$ less oxygen than the precipitation effluent which 
was applied to it. 

The life of a contact filter cannot yet be stated definitely; 
but if no insoluble mineral matter reaches it, and if it is not 
overworked, it should continue to act indefinitely. Soft coke, 
and still more burnt clay, have a tendency to disintegrate and 





DESTRUCTION . 


423 


clog the filter. If it becomes clogged by these or by sewage 
matters it is necessary to refill it with fresh filtering material. 
At Winsford, England, what is practically a contact filter has 
been in operation for over twenty years and is apparently in 
as good condition as ever. 

The first or anaerobic action is secured by the septic tank 
also, in which the anaerobes almost entirely liquefy the sew¬ 
age, although very fine particles of matter in suspension are 
generally carried away by the effluent. To prevent sand and 
other insoluble matter from gradually filling the tank a sand 
intercepter is necessary. If this acts effectively almost no 
sludge collects. The septic tank consists essentially of a 
rectangular tank through which the sewage flows continuously, 
and so slowly as to permit all suspended matters to settle to 
the bottom or collect upon the surface, the sewage being 
drawn off by a horizontal slot a foot or so below the surface. 
The floating matter forms a scum from two or three to thirty 
inches thick, which teems with bacteria. The size of the tank 
varies in different plants, capacities of from one-fourth to 
twice the sewage flow per 24 hours having been given. 
Probably the majority have a capacity of about the daily flow. 
It was at first thought necessary to exclude air and light from 
the tank by means of a roof or cover, but the experiments at 
Lawrence and Manchester have shown this to be unnecessary.* 
It is thought desirable, however, to cause the sewage to enter 
the tank beneath the surface of its contents, that air may be 
excluded; and the scum probably serves to exclude both 
light and air from above. The depth of the tanks which have 
been built varies from 3! to 10 feet. Since the scum may 
occupy two feet or more, and the sediment half this depth, 
it would seem desirable to make the tank at least 5 feet deep, 
and probably 6 or 8 feet would be better. Too great depth 
or width will render it difficult to cause uniform flow through- 

* Further investigations during 1901 have confirmed this. 


\ 




4 2 4 


SE WEE A GE. 


out the tank, which is essential. The areas of the tanks vary 
from 16 x 37 feet to iS X 100 feet. 

In the reduction of the organic matter about 25 <f> is 
changed to hydrogen, marsh-gas, free nitrogen, and carbonic- 
acid gas; part of which are held in suspension in the sewage, 
the remainder being given off into the air. For this reason it 
may be desirable to cover large, and even small, tanks to pre¬ 
vent the gases from creating a nuisance; although the foulest 
odors seem generally to come from the effluent rather than 
from the tank itself. In a few plants these gases are collected 
and burned, being highly inflammable. 

The gases contained in the effluent are objectionable not 
only because of their odor, but also because they inhibit sub¬ 
sequent aerobic action. It is therefore desirable to remove 
them before the second stage of purification, which is ordi¬ 
narily effected by passing the effluent over a long weir, or 
spraying it in some way. 

In 1897 the Exeter septic tank was found by six different 
observers to effect a reduction in the albuminoid ammonia of 
from 63.2$ to 84.9$, and in oxygen consumed of from 78.7$ 
to 90 fo, crude sewage being treated. 

At Champaign, Ill., a septic tank 37 X 16 X 5 feet deep 
(see Fig. 38) purified the sewage from 3500 persons, together 
with 100,000 to 300,000 gallons per day of ground-water, 
with the result shown on page 426. 


An open septic tank whose effluent was treated by double 
contact at Manchester, Eng., gave the following average 
purification during ten consecutive weeks: 


Effluent from 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia. 

Putrescibility. Per cent, 
passing Incubator Test. 

Open tank. 

7.00 

O.31 

O 

First-contact bed. 

2.21 

0.150 

50 

Second-contact bed. 

O.69 

0.064 

IOO 















DESTRUCTION. 


425 


Experiments have appeared to indicate that typhoid 
bacilli, and probably other pathogenic bacteria, are killed by 
the gases, anaerobes, or enzymes connected with anaerobic 
action. 

The gas in the top of the Champaign tank was found to 
consist of: Carbonic-acid gas, 10.7$ by volume ; free nitrogen, 



Fig. 38—Interior of Champaign, III., Septic Tank. 

(From Engineering A T ews.) 

27.8$; marsh-gas, 55.3$; and ethane, 6.2 <? 0 ; the mixture be¬ 
ing highly inflammable. The gas in the Exeter tank con¬ 
tained 0.6% carbonic-acid gas; 38.6$ free nitrogen; 24.4$ 
marsh-gas; and 36.4 % hydrogen. 

The sludge at the bottom of the Champaign tank was 
found to be composed of: Water, 60.9$; organic matter, 4.7$; 
inorganic matter, 34.4^. The floating scum contained 92$ 
moisture; 3 organic matter; and 5% inorganic matter. 

The septic tank at Verona, N. J., 18 X 5 ° X 10 feet deep, 
together with two filters 70 X 30 and 80 X 30 respectively, 
cost $4000 for construction. A tank at Wauwatosa, Wis., 
handling 100,000 gals, per day cost $5370; one at Lake 
Forest, Ill., with a capacity of 200,000 gals, per day cost $8ooc. 







ANALYSES OF SEWAGE AND OF EFFLUENT FROM SEPTIC TANK, CHAMPAIGN 


426 


SEWERAGE. 









• 

• 

• 

• 


O 

0 

O 

0 

•—1 

0 

• 

• 

• 

• 

•Xauapyja 


CO 


O' 

"f 

O' 

• 

• 

• 

• 


O' 

C 4 

O' 

HH 

O' 


• 

• 

• 

• 

• 

• 

• 







• 


• 

• 

>> 

cd 


ro 

M 

00 

co 

10 

0 

• 

• 


• 


•ADlI 3 I 0 ^f-q 

VO 


0 

d 

vo 

CO 

• 

• 



V- 


O' 

M 

O' 

HH 

O' 

•—I 

• 

• 



O' & 














0 

O 

0 

0 

04 

co 

O 


0 

O 


U 

VO 

»—< 

Cl 

co 


O 

0 

0 

O 

CO° 

juanmg 

M 

IT) 

0 

0 

0 

• 0 

VO 

0 

VO 

O 

>* re 


6 

o' 

d 

d 

d 

0 

d 

d 

d 

VO 

rt be 












0 



0 


O' 

o- 

O' 

0 


0 

0 

8 


a 


0 

M 

0 

CO 

- 1 - 

O 

0 

0 

6 

• 3 SbM 3 § 

»—t 

0 

co 

O 


0 

0 

O 

-r 


O 

rf 



d 

d 

d 

d 

d 

0 

o’ 

d 

U-» 

. 











. 



0 

to 

M 

VO 

0 



• 


• 

cd 

Aouapy^a 

0 

CD 


O' 

r» 



• 


; 

O' V- 

00 <u 


0 

Cl 

O' 


O' 



• 

• 


1 














0 

0 

0 

CO 

0 


0 

O 

VO 

0 



VO 

t—> 

HH 

<0 

T 


0 

03 

T'- 

0 

ti 

uianyja 



O 

0 

0 


vC 

W 

CO 

O' 

cd 


6 

d 

d 

d 

d 


d 

d 

d 

4 

u te 












•g 0 


0 

0 

0 

Cl 

Cl 


0 

0 

0 

0 

, w 9 


\n 

vo 

m 

’t 

10 



0 

0 

0 

U, 0 . 

6 

3 Sba\ 3 S 

O' 

O' 

in 

0 

CO 


0 

a 

00 

O' 

10 

« 


to 

d 

6 

6 

►H 


d 

0’ 

d 

* 1 " 

. 












>> 


O 

0 

O' 

co 

O' 

0 




• 

• cd 

00 

O' 

Xouaptya 

6 

O' 

0 


O' 

d 





00 v- 

M 

. Cl 
w 


O' 

Cl 

00 

co 

CO 







0 

0 

Cl 

Cl 

Cl 

CO 

CO 

VO 

VO 

0 

CN 2 


hH 

Cl 

CO 

co 


CO 

CO 

c» 

Cl 

0 

u S 

V £ 

aaanyja 

co 

0 

0 

0 

0 

0 

Cl 

M 


0 

•5 cd 


6 

d 

d 

d 

d 

d 

d 

d 

d 

VO 

£ be 














0 

0 


M 

Cl 

CO 

Tf 

0 

vo 

O 

1 0 s 



00 

HH 

vo 

M 

CO 

0 


Cl 

O 

£ o' 

• 3 §BM 3 S 


00 

co 

0 


0 

CO 

M 

-t 

0 

0 

VO 

| 

co 

d 

d 

d 

o’ 

d 

d 

d 

d 

VO 


; 


0 

• 

0 



• 

• 

• 

• 


• 

: 



• 

O 

• 



• 

















• 

in 




• 






• 

c 

0 

_o 


• 

• 

• 







CL 

w 



• 







in 

3 



• 





I \ 


P 

in 

'd 

• 

• 






. 


75 










c 

f - 1 

c 









<—< 


0 











7 ] 

3 






c 




0 

O 






! 0 




V 







in 

0 

c 

0 


a 

in 









c 


3 

O 






«—* 



in 

73 


• 




CL 

3 

c 



• 




!e 


t—■ 


c 

c 

cd 

• 




3 

0 

cd 


HH 

»-H 






- n 

w 

2 


0 


s 

0 

• 

• 


• 


In 


0 


0 


E 



in 




c 


to 


c 

in 

V 

73 

V 


■0 


E 


0 

U 


cd 

V 

4—» 

T 3 


E 


0 


w 

E 


0 

V 

w 

cd 

w 

u 

^0 


P 

7 ) 


3 


CJ 


u 

c 


-C 

0 


c 

0 


in 

cd 


s 

3 


73 


« 

c 

• »-h 


0 

c 


c 

0 


bo 

u 

0 


c 

0 



u 

c 


CJ 


tc 




u 





tc 


0 




0 

• 


U 


>> 


U 

w 


cd 
•*—> 


U 



O 




• — • 


0 





J 3 


0 




f-H 





u 















































































DESTRUCTION . 


427 


The Champaign and Urbana septic tanks were designed 
almost simultaneously with the Exeter tank, but entirely 
independently, by Prof. A. N. Talbot in 1894. The same 
principles were involved in the Mouras Automatic Scavenger, 
invented about i860, but they were not understood and the 
scavenger never came into general use. 

The advantages of the septic tank as compared with the 
contact filter are : That sludge or matter resisting liquefaction 
can be more readily removed; that the effluent is continu¬ 
ously of a quite uniform character, thus preventing periodical 
excessive demands upon the subsequent filtration-beds; that, 
the inlet and outlet being at practically the same level, the 
tank occasions little loss of grade; and that the flow through 
the tank is continuous. Its chief disadvantage lies in the odor 
connected with the tank and effluent, and the difficulty of 
nitrifying the latter. It is also thought that the filtering ma¬ 
terial of a contact bed affords lodging-places for more bacteria 
than does a septic tank. fSee also Appendix III.) 

The second stage of purification is almost invariably a fine- 
grain filter or a contact filter; the chief difference between 
these being that the former relies upon capillary attraction to 
prevent the too rapid passing of the sewage through the filter, 
the latter upon a valve in the outlet-pipe. In both the action 
should be wholly or largely aerobic. There is, however, the 
difference that a fine-grain filter seems able to remove a much 
larger percentage of the bacteria than can a contact filter. 

The surface of the secondary filter must generally be below 
the level of the outlet from the primary filter or tank, and its 
outlet must be the depth of the bed below its surface, if the 
filters act intermittently. One advantage connected with 
continuous-flow filters is that the total drop in grade through 
the filtration plant need not exceed a few inches, while with 
intermittent filters the drop must equal the sum of the depths 


428 


SEWEKAGE. 


of both filters. This last fact will in many cases place a limit 
upon the depth of intermittent filters; and as their depth is 
decreased their area must be increased. 

i 

Art. 99 . Other Purification Methods. 

Several methods of purifying sewage other than those 
already named have been tested, most of them merely utiliz¬ 
ing different details of structure or treatment in the applica¬ 
tion of bacterial action. Col. Ducat constructs his filter-bed 
with porous walls and bottom, with the idea of supplying 
more oxygen for nitrification. The large amount of outer 
air entering this filter in winter cools the sewage below the 
temperature favorable to bacterial action, and must then be 
artificially heated. 

In 1898 Whittaker and Bryant constructed a “thermal 
aerobic filter” at Accrington, Eng., somewhat similar to 
Ducat’s in construction, but in which jets of steam sprayed 
into the sewage raise the temperature in both summer and 
winter to that most favorable to bacterial action. 

Lowcock places in a sand filter a layer of coarse gravel at 
about one-third its depth from the top, and lays through this 
gravel a number of perforated pipes through which a blower 
forces air continuously, and the mingled air and sewage pass 
downward through 4 feet of coke or gravel to sub-drains; 
only a slight pressure being required in the blower. The 
object of this construction is to render unnecessary the resting 
and aerating of sand filters. The same result was the aim of 
Col. Waring, who established at Willow-Grove Park, Phila¬ 
delphia, and at Homewood, Brooklyn, filters in which the air 
is forced through porous tile laid in the bottoms of the filters; 
the former plant treating strained sewage at the rate of 
640,000 to 800,000 gallons per acre daily; the latter treating 
245,000 gallons per acre of strainer and filter combined. 


DESTRUCTION. 


429 


Art. 100. Summary. 

No generally applicable rule can be laid down for selecting 
a method of treatment best adapted to any particular locality. 
This method will depend upon the character of the sewage, 
the degree of purification desired, the location and surround¬ 
ings of the city, the character of the soil, cost of land, and 
other considerations. Sewage strongly impregnated with 
gas-house waste, for instance, or with highly acid refuse, 
needs preliminary treatment before thorough nitrification can 
be accomplished. If the effluent discharges into tidal waters, 
a much lower degree of purification is demanded than if a 
potable river be its destination. If the city is closely sur¬ 
rounded with residence suburbs, or is on a clayey, marly, or 
rocky soil, or if all land in the vicinity is very expensive, 
irrigation or intermittent filtration without previous treatment 
is probably impracticable. 

If it is desired merely to prevent a nuisance, rapid filtra¬ 
tion, chemical precipitation, a septic tank, or a coarse 
bacteria-bed may be sufficient; while if the effluent must be 
discharged into a potable stream, the filtration must be slow 
and through fine material, or the other methods of partial 
purification must be supplemented by slow sand filtration, or 
by careful treatment in a fine bacteria-bed. 

It has been argued that a nuisance may be avoided if all 
organic matter in the effluent be in solution or very finely 
divided, and if the “oxygen required” by the total dis¬ 
charge during any hour be no greater than that contained 
free and in the form of nitrates in both the effluent and the 
river-flow during that hour. This assumes a complete inter¬ 
mixing of water and effluent, and it is probable that the 
dilution proposed on page 26 is a more reliable standard. 

Which of several systems, all producing an acceptable 
effluent, should be selected will be largely a question of cost, 


430 


SEWERAGE. 


the decision of which can only be settled in each case by a 
study of the local conditions and the prices of materials and 


labor, both for construction and for maintenance. 

No method of treatment is entirely automatic, but all 
need intelligent care. Bacteria require as regular attention 
in the way of food, air, and heat as do any farm stock; and 
a careless superintendent can in one week destroy bacterial 
conditions which it will take months of careful attention to 
replace. 











APPENDIX. 


430 a 


The following table gives a list of sewage-treatment plants 
in cities and towns of the United States having 3,000 popu¬ 
lation or more. From the Mimicipal Year Book for 1902 ; re¬ 
arranged and extended by the author. 

Table No. 30. 

SEWAGE-TREATMENT PLANTS IN THE UNITED STATES. 


INTERMITTENT FILTRATION. 
Total Number, 30. 


BROAD IRRIGATION, SEWAGE FARMING 
OR OTHER LAND DISPOSAL. 

Total Number, 27. 


Town or City. 

L 


Population. 


Town or City. 


Population. 


* Worcester, Mass.. 

Houston, Tex. 

Brockton, Mass.... 
Pawtucket, R. I,... 

f Altoona, Pa. 

Woonsocket, R. I. . 

Meriden, Conn. 

Pittsfield, Mass 
Central Falls, R. I. 
Danbury, Conn . .. 
X Plainfield, N. J.... 

Clinton, Mass. 

Marlboro, Mass.... 
Framingham, Mass 

Gardner, Mass. 

Manchester, Conn . 
Southbridge, Mass. 

Natick, Mass. 

Paris, Tex. 

Spencer, Mass. 

Andover, Mass.... 
Bristol, Conn .... 

Concord, Mass. 

Westboro, Mass ... 

Summit, N. J. 

Franklin, Mass. 

Oberlin, O . 

Ripon, Wis. 

Mendota, Ill. 

Leicester, Mass.... 


118,421 

44.633 

40,063 

39,231 

38,973 

28,204 

24,296 

22,037 

18,167 

16,537 

15,369 

13,667 

13,609 

11,302 

10,813 

10,601 

10,025 

9,488 

9,358 

7,627 

6,813 

6,268 

5,652 

5,400 

5,302 

5,oi7 

4,082 

3,8i8 

3,736 

3,4i6 


f Los Angeles, Cal. 

Salt Lake City. 

§ Altoona, Pa. 

Colorado Springs....... 

§ Framingham, Mass.... 

Sherman, Tex. 

Walla Walla, Wash. 

Pasadena, Cal. 

Fostoria, O... 

Tucson, Ariz. 

Hastings, Neb. 

* Santa Rosa, Cal. 

Columbia, Mo. 

Phoenix, Ariz. 

|| Pomona, Cal. 

Brookfield, Mo. 

Bakersfield, Cal. 

Redlands, Cal.... 

Red Jacket, Mich. 

North Brookfield, Mass.. 

McKinney, Tex. 

Oberlin, O. 

Princeton, N. J. 

Raton, N. M. 

St. Johns, Mich.... 

Visalia, Cal. 

Greeley, Colo. 


102,479 

53,53i 

38,973 

21,085 

11,302 

10,243 

10,049 

9.117 

7,730 

7,53i 

7,188 

6,673 

5,651 

5,544 

5,526 

5,484 

4,836 

4,797 

4,668 

4,587 

4,342 

4,082 

3,899 

3,540 

3,383 

3,085 

3,023 


* Also chemical precipitation, 
t Part of the sewage only. 

X Also septic tank and contact beds. 
§ Also intermittent filtration. 

0 Also septic tank. 





































































APPENDIX. 


430 b 


Table No. 30. — Continued. 


SEWAGE-TREATMENT PLANTS IN THE UNITED STATES. 


CHEMICAL PRECIPITATION. 
Total Number, 9 . 


Town or City. 

Population. 

Prnvifipnre. R. L. 

175,597 

118,421 

* Wnrrpstpr. Mass. 

26th Ward. Brooklyn... . 

Canton O. 

30,667 

14,720 

8,974 

7,899 

6,673 

5,588 

Now Rochelle N.Y. 

Alliance O..... 

White Plains N. V. 

4 Santa Rosa . Cal. 

t Glenvil 1 e O. 


SEDIMENTATION. 

Total Number, 5. 

* Central Falls, R. I. 

Boulder. Colo. 

18,167 

6,150 

6,105 

5,345 

5,028 

Paris, Til. 

Trinidad, Colo. 

Amherst, Mass. 

COKE OR SAND FILTRATION. 

Total Number, 8. 

Reading. Pa. 

78,961 

7 , 4 i 9 

7,392 

5,588 

4,685 

4,370 

A 099 

S Waukesha, "Wis. 

Burlington, N. J. 

| Glenville, O. 

Shelby, O. 

Vineland N. J. 

8 Princeton. Til. 

Aiken, S. C. 

3,414 



STRAINING. 
Total Number, 2 . 


Leadville, Colo.... 
Long Branch, N. J. 


12,455 

8,872 


* Also intermittent filtration, 

t Also broad irrigation. 

X Also coke and sand filters. 

§ Also septic tank. 


SEPTIC TANKS. 
Total Number, 34 . 


Town or City. 


I* * * § *Worcester, Mass.... 

* Pawtucket, R. I. 

1"** Kingston, N. Y. 

* Madison, Wis. 

** Mansfield, O. 

* ** Plainfield, N. J. 

** Fond du Lac, Wis 

** Marshalltown, la. 

Champaign, Ill. 

Kewanee, Ill. 

** Delaware, O. 

ff Holland, Mich. 

* Waukesha, Wis. 

* Independence, Mo. 

* Andover, Mass. 

DeKalb, Ill. 

Urbana, Ill. 

f Pomona, Cal. 

** Red Bank, N. J. 

Macomb, Ill. 

** Danville, Ky. 

Marion, la. 

* Princeton, Ill. 

La Grange, Ill. 

Depew, N. Y. 

Lakewood, O. 

San Luis Obispo, Cal.. 

Lake Forest, Ill. 

Glen View, Ill. 

Highland Park, Ill. 

Wauwatosa, Wis. 

* Liberty, N. Y. 

Hopedale, Mass. 

Verona, N. J.. 


Population. 


11 Also chemical precipitation. 
1 Part of the sewage only. 

** Also contact beds, 
ft Also coke strainer. 


118,421 

39.231 

24.535 

19,164 

17,640 

15,369 

15,110 

H.544 

9,098 

.8,382 

7,940 

7,790 

7,419 

6,974 

6,813 

5,904 

5,728 

5,526 

5,428 

5,375 

4,285 

4,102 

4,023 

3.969 

3,379 

3,355 

3,021 


I 

























































































APPENDIX, 


43 cx 


Table No. 31 . 

DENSITY OF POPULATION, CITIES OF 100,000 AND UP, 1890. 

(AVERAGE AND MAXIMUM.) 

(From the U. S. Census of 1890.) 



Per Acre. 

Persons per 

City. 

Dwellings. 

Persons. 

bi 

_c 

"w 

■s 

Q 

Family. 

Allegheny. 

325 

20.66 

6.36 

5.06 

3d Ward. 

13-57 

93-63 

6.90 

4.70 

10th Ward. 

°-55 

2.88 

5.22 

5.02 

Buffalo. 

1.49 

10.65 

6.86 

4-97 

2d Ward... 

7.71 

61.80 

8.02 

5-84 

12th Ward. 

0.21 

i -34 

6-33 

5 . 8 i 

Chicago . 

1.24 

IO.7O 

8.60 

4-99 

16th Ward. .. 

8.07 

117.27 

14.52 

4.78 

Cincinnati. 

2.26 

20.02 

8.87 

4.67 

7th Ward. 

12 . IQ 

154.88 

12.71 

4.08 

Cleveland. 

2-75 

16.41 

5-96 

4-93 

10th Ward.... 

8-95 

50.31 

5.62 

4 85 

Detroit. 

2.81 

15-63 

5-57 

4.88 

3d Ward. 

5-24 

29.97 

5-72 

4.61 

Indianapolis. 

3-°3 

15.14 

4-99 

4-57 

23d Ward. 

7.69 

37.22 

4.84 

4.64 

Jersey City. 

2.23 

19.59 

8.78 

4-73 

3d District. 

13-75 

151-01 

10.98 

4-79 

Kansas City . . 

1.11 

6.39 

5-74 

4.96 

6th Ward. 

6.12 

39-93 

6.52 

5-05 

Louisville, Ky... 

3.16 

20.36 

6-45 

4.89 

3d Ward. 

6.01 

40.04 

6.66 

4-49 

Milwaukee. 

3.02 

18.79 

6.22 

4.92 

2d Ward. 

6.23 

42.53 

6.82 

4 - 7 i 

Minneapolis.... 

0.76 

4.98 

6.52 

5 -oi 

6th Ward. 

5.12 

38.14 

7.46 

4.96 

Newark. 

2.05 

15-99 

7.81 

4.67 

15th Ward. ... 

7.92 

63.08 

7.96 

4-37 

New Orleans.... 

1.81 

10.20 

5-63 

4.98 

6th Ward. 

8.77 

56.26 

6.41 

5.28 

New York . 

10th Ward. 

13.60 

523.6 

18.52 

38.5 

4.84 

4.90 

Philadelphia.. .. 
Pittsburg. 

2.17 

13-75 

5.60 

6-33 

5-23 

7th Ward. 

19.02 

137.26 

7.22 

5-21 

St. Louis. 

*■55 

n.50 

7.41 

4.92 

8th Ward.. 

14.34 

143-25 

9-99 

4-25 

St. Paul. 

0.64 

4.05 

6-35 

5 -iS 

4th Ward. 

5 - J 4 

42.57 

8.28 

5-76 

Fall River. 



11.02 



Business section; residents of good class. 

Residences of mechanics on high ground. 

Mostly business; many hotels and tene¬ 
ments. 

Suburbs, good class of laborers; park, 
cemeteries, etc. 

Polish and German artisans and laborers. 

Centrally located; good class of Germans. 

Dense population of laborers in cheap 
tenements; 77 acres; contains cemetery. 

Business and manufacturing; railroad 
yards; negroes, French, Italians, Poles, 
and Germans. 

No description given. 

Residents of moderate means. 

Mostly good class of residents. Some 
Italians and cheap tenements. Gas¬ 
works. 

Mostly Germans. Two breweries, market, 
woolen mill. 

Mostly Germans; some Russians and ne 
groes; brewery and small factories. 

Mechanics, laborers, railroad employees; 
small section of cheap tenements. 

Irish tenements; a few Italians; a number 
of shoe factories. 

No description given. 


Good class of residents. 

Tenements; Russians, Poles, negroes, 
Italians, Bohemians. Low class of pros¬ 
titutes. 

Business, hotels, tenements; State Capitol, 
county court-house, and prostitutes. 


































































APPENDIX I. 


Since the publication of “Sewerage” the author, in 
reply to inquiries made by him, has received from ninety-four 
city and sanitary engineers in thirty-three States reports upon 
the ventilation of sewers, trapping of inlets and house-con¬ 
nections, and use of catch-basins. 

Of 27 house-sewer systems, 12 are provided with main 
traps on the house-connections, 15 are not. Of 36 combined 
systems, 32 are provided with main traps on house-connec¬ 
tions and 4 are not. Of the 19 cities omitting main traps, 
but one, and that one sewered on the combined system, finds 
such omission objectionable. 

Of 37 storm-water systems, 18 are provided with catch- 
basins under all their inlets, 7 under none, and 12 under a 
part only of the inlets. Of 40 combined systems, 26 are 
provided with catch-basins under all inlets, 3 under none, 11 
under a part only. 

Of 37 storm-water systems, 13 have all the inlets pro¬ 
vided with traps, 17 none, and in 7 a part only of the inlets 

N. 

are so provided. Of 43 combined systems, 26 are provided 
with traps on all inlets, 3 on none, and 14 on a part only. 

0 

Of 23 house-sewer systems, 7 are ventilated through 
manholes only, one through house-connections only, and 15 
through both. Of 28 storm-sewer systems, 22 are ventilated 
through manholes only, none through inlets only, and 6 
through both. 

Of 40 combined systems, 2 are ventilated through inlets 
only, 25 through manholes only, 10 through both inlets and 

431 


432 


SEWERAGE. 


manholes, and 3 through both manholes and house-connec¬ 
tions; while 2 have no ventilation provided, and one uses 
electric-light poles. 

Of much more value would be a comparison of the 
efficiency of each of these practices, especially where all are 
used in the same system and are thus more fairly comparable. 
Unfortunately few replies contained such information. Of 15 
house-sewer systems ventilating through both manholes and 
house-connections, in but one was the practice found objec¬ 
tionable, and in this only where but a few house-connections 
were so constructed and the combined system was used. 
Five cities with storm-sewer systems, one with a house-sewer 
system, and three with combined systems found ventilation 
through manholes only to be inadequate. In most of the 
Northern cities there are weeks at a time when most or all of 
the manhole ventilation-openings are sealed with ice or 
snow. In most States clay frequently produces the same 
result. Twenty-eight cities find inlet-traps unsealed more or 
less frequently; five do not. In a few cities in the far West 
inlet-traps are unsealed for weeks and even months at a time 
during the dry season. 

Most interesting were the opinions upon ventilation and 
catch-basins expressed by many of the engineers. By a con¬ 
siderable majority of these, catch-basins were considered 
objectionable, or at least unnecessary, except where consider¬ 
able gravelly or sandy soil was washed into the inlets from 
unpaved streets. By a somewhat smaller majority traps 
upon inlet-connections were considered undesirable; several 
of these, however, advocating their use with combined sewers. 
A large majority agreed that ventilation of sewers through 
manholes was unsatisfactory, and most of these advocated 
omitting traps on inlets to assist the ventilation; while a small 
majority believed the universal omission of main-traps on 
house-connections to be advisable. 


APPENDIX II. 


FOLLOWING is a list of references to the statutes of twenty- 
two States referring to the POLLUTION OF WATER : 

California. Criminal Code (1886), Secs. 1357, 1376. 
Connecticut. General Statutes (1888), Secs. 2652-5. Chap¬ 
ters 28 and 203 of 1895. 

Delaware. Revised Code (1893), p. 926. Delaware Laws, 
Vol. XII, Chapter 405. 

Illinois. Annotated Statutes (1896), Chapter 38, Secs. 369 
(2), (3); Chapter 24, Art. 10, Sec. 2. 

Indiana. Statutes (1897), Secs. 2017, 2195. 

Iowa. Code (1897), Sec. 4979. 

Kansas. General Statutes (1897), Chapter 100, Secs. 338-9. 
Kentucky. Statutes (1894), Sec. 1278. 

Maine. Chapter 82 of 1891. 

Maryland. Public General Laws (1888), Vol. I, p. 550, Sec. 
277. 

Massachusetts. Public Statutes (1882), Chapter 80, Secs. 
96-7, 101-2. Chapter 208, Secs. 7-8. Chapter 172 of 
1884. Chapter 274 of 1886. Chapters 160 and 375 of 
1888. 

Michigan. Compiled Laws (1897), Sec. 11,432. 

Minnesota. Statutes (1894), Secs. 430-1, 6642. 

New Hampshire. Public Statutes (1891), Chapter 108, Secs. 

13-15. Act of March 28, 1895. 

New Jersey. General Statutes (1895), p. 1644, Sec. 49; (XII) 
pp. 1107, 1109, 2215. 

New York. Revised Statutes (1895), p. 2437, Secs. 70-72 d. 


433 


434 


SE WEE A GE. 


North Carolina. Act of March I, 1893, 18-21. 

Ohio. Annotated Statutes (1900), Secs. 409, (26), 6921, 
6923, 6925. 

Oregon. Annotated Laws (1892), Sec. 198. 

Tennessee. Code (1896), Sec. 6869. 

Virginia. Code (1887), Sec. 3812. Chapter 460 of 1892. 
West Virginia. Code (1899), Chapter 150, Sec. 20 & and c. 


1 


l 



APPENDIX III. 


THE MANAGEMENT OF SEPTIC TANKS AND BACTERIAL 

CONTACT BEDS. 

(Condensed from a paper presented to the Royal Institute of Public Health by 
Gilbert J. Fowler, Superintendent and Chemist of the Sewage Disposal Works, 
Manchester, England, 1901.) 

The Management of Septic Tanks. —The objects of 
careful management of septic tanks will be: (i) To dissolve 
or gasify as much sludge as possible. (2) To obtain a tank 
effluent in which the matters in solution are easily nitrified. 

(3) To produce a tank effluent with little suspended matter. 

(4) To avoid creating a nuisance. 

Destruction of Sludge in Septic Tank .—It must always be 
remembered that no bacteria have yet been discovered which 
will consume mineral matter. In all cases, therefore, where 
road detritus is mixed with the sewage, ample catch-pit accom¬ 
modation should be provided. Having provided grit chambers, 
it is necessary that they should be cleared out at frequent 
intervals, or they cease to be catch-pits. If the catch-pits are 
too small, all the grit will not be arrested ; if too large, sludge, 
which might otherwise have been bacterialized, will be taken 
away with the grit. Besides grit, it is, in my view, well to 
screen out bits of wood, rags, etc., as such cellulose material 
is only very slowly attacked in the septic tank. 

Having removed insoluble substances from the sewage, it 
will be possible to obtain a higher percentage of destruction in 
the septic tank. It will be found, on starting a new septic 
tank (as in the case of a bacteria bed), that the action begins 

435 


* 


436 


SEWERAGE. 


slowly, and gradually arrives at a maximum. It is important, 
therefore, that the ultimate flow should not be passed through 
the tank at first, lest sludge should rapidly accumulate before 
septic action is established. When one septic tank is fully at 
work, another may easily be started by pumping into it enough 
sludge from the first to just cover the bottom. 

Production of Easily Nitrified Effluent from Septic Tank .— 
It must be emphasized, in dealing with this point, that by no 
means the least important function of the septic tank is to so 
change and break down the soluble constituents of the sewage 
that these are readily nitrified when put upon bacteria beds. 
Even if but little reduction in sludge took place, this action 
alone would justify the use of septic tanks. 

If the flow through the septic tank is suddenly increased 
during a time when the sewage is at full strength, fresh sewage 
may find its way on to the beds, and will fail to be purified; 
for it has been definitely established that beds which have 
become accustomed to septic sewage will not at once purify 
fresh sewage, and vice versa. Apparently unaccountable 
changes in the efficiency of bacteria beds may sometimes fie 
traced to this cause. An increased flow of sewage, diluted by 
rain, may be safely put through, as in this case the proportion 
of organic matter per gallon will be less. 

It is also quite possible, I believe, to work a septic tank 
too slowly, and produce a putrid effluent which is actually 
poisonous to the nitrifying organisms. Possibly some com¬ 
plaints of the nuisance arising from septic tanks may be due to 
this cause. The exact rate of flow to be adopted will depend 
on local conditions. 

Avoidance of Nuisance. —A good deal of apprehension has 
been expressed as to the possibility of nuisance arising from 
septic tanks, and it is certainly a matter for serious considera¬ 
tion. The residual sludge and grit can be pressed and used 
for manure or burnt. The silt alone is quite innocuous, and 


APPENDIX III. 


437 


if tipped (used for filling) is rapidly converted into a dry, sandy 
heap. Covering the tank is not a real prevention of the 
nuisance, unless the gas evolved is collected and burnt. In 
Manchester, Leeds, Accrington and other places, however, 
there is singularly little odor, either from the open tank or from 
the sludge. 

Management of Contact Beds. —The management of 
contact beds should be directed toward: (i) The production of 
a pure effluent. (2) The maintenance of capacity. (3) The 
minimum expenditure of labor. 

Production of a Pure Effluent .—One of the chief factors in 
producing a good contact-bed effluent or filtrate is the absence 
of great variation in the composition of the septic-tank effluent. 
It will be more completely achieved if manufacturers can be 
induced to send down their refuse in a steady stream, and not 
in intermittent flushes. In most cases there is little difficulty 
in obtaining their co-operation to this end. It is often to their 
advantage that their trade refuse should be under careful super¬ 
vision, as unsuspected sources of waste are often discovered by 
this means. 

The thorough drainage of a bacteria bed is of the first 
importance in securing a good effluent. If the water cannot 
get out, the air cannot get in, and the lower parts of the bed 
rapidly become putrid and the nitrates decrease, perhaps are 
quite absent. It must be emphasized that when the nitrates 
decrease, and simultaneously there will always, as a rule, be 
an increase of nitrites, the bed must be rested. 

With experience, a modification of the three minutes 
oxygen absorption test may be adopted as an index to the 
efficiency of the bed, which may be put in the hands of a 
workman to carry out. For a given sewage there is generally 
a pretty constant relation between the three minutes oxygen 
absorption test and the other determinations, ammonias, 
nitrates, etc. If an acid solution of permanganate of known 


438 


SEWERAGE. 


strength is made up in the laboratory and given to the filter 
foreman, with a measuring glass, by mixing known quantities 
of the contact-bed effluent and the permanganate solution he 
can readily ascertain the character of the effluent by the 
rapidity with which the permanganate is discolorized. 

Maintenance oj Capacity .—It is quite possible for the 
effluent from the bed to continue excellent in composition 
although the bed may be falling off very much in capacity. 
Careful note must therefore always be made of the time of 
filling under identical conditions, if more accurate methods of 
measurement are not available; and if it begins to rapidly 
decrease, the bed must be rested. 

The chief causes of less capacity are the following: (a) 
Settling together of the material. ( b ) Growth of organisms. 
(<:) Impaired drainage. ( d ) Solid matter entering the bed. 
(<?) Breaking down of material. 

(a) Settling Together of Material.—This must always occur, 
and largely accounts for the initial rapid decrease in capacity 
after the bed has been at work for a short time. It may, 
indeed, often be necessary to put an additional quantity of 
material upon the bed to maintain the surface at its original 
level. 

(b) Growth of Organisms.—This is at once the cause of 
increased efficiency in the bed and of loss of capacity. On 
examining the material of a contact bed in active condition, 
every piece of it, clinker, coke, whatever it may be, will be 
found coated over with a slimy growth. If this is removed it 
is found to be a stiff jelly which, after a little drying, can be 
cut with a knife. Before examining under the microscope, it 
should be treated with dilute acid to remove as much as possi¬ 
ble of any hydrated oxide of iron present. It is then seen to 
consist largely of masses of bacteria and zoogloea. If placed 
in a tube containing air, and connected with a manometer, the 
jelly will rapidly absorb all the oxygen with production of 


APPENDIX III. 


439 


carbon dioxide. This action will sometimes produce a vacuum 
equal to several inches of mercury. This experiment shows 
that there is little need to force air into a bed. As a matter 
of fact there is always a large amount of oxygen to be found 
at the bottom of a bed in good condition, owing to the inter¬ 
change of gases which naturally takes place. The behavior of 
the bacterial jelly appears to afford the clew to the successful 
working of bacteria beds. By working them at high speed, 
i.e., filling them frequently in the day without long periods of 
rest, the effluent may remain good, but the bacterial growth 
so rapidly increases that the bed becomes too spongy and will 
not allow the water to drain away. Here, too, is the expla¬ 
nation of the fact that, within limits, decrease of capacity 
is accompanied by increase of efficiency. This decrease of 
capacity may, however, become so great as to more than out¬ 
weigh the advantage of increased efficiency. A long period, 
say one or two weeks’ rest, must then be given to the bed. 
The superfluous bacterial growths will, during this time, be 
rapidly consumed, and the capacity of the bed will greatly 
increase. Increase of capacity due to this cause is not a 
merely temporary phenomenon, produced by the drying of the 
bed. One of the Manchester experimental beds, for instance, 
sank in capacity during the winter of 1899-1900 to such a low 
point as 1480 gallons (the capacity at the beginning of the 
experiment being 4200 gallons). At the present time, after 
fifteen months have elapsed, during which the bed has been in 
regular use, its capacity under similar conditions of measure¬ 
ment is 2000 gallons, and it has not yet reached its full summer 
capacity. This result has been brought about simply by 
judicious periods of rest. It has been found in the course of 
experiment that these should not exceed a fortnight at most, 
as the bed then tends to dry up, and the activity of the 
organisms diminishes. 

These results cause me to think that the policy of pushing 


440 


SE WEE A GE. 


the working of the bed to its utmost extent and frequently 
washing the material, as recommended by Dr. Dunbar, of 
Hamburg, is not really satisfactory. By washing the material 
the bacterial jelly is removed, and will have to be reformed 
before the bed is completely efficient. The time spent in 
washing, if given to resting the bed, would probably produce 
a rise in capacity almost equal to that possessed by the bed 
after the initial period of slow working required for regaining 
efficiency. 

(c) Impaired Drainage.—-This matter has already been 
dealt with in speaking of the causes which tend to deteriorate 
the effluent. It cannot be too strongly emphasized that every 
care should be taken in designing the bed to make the drainage 
as efficient as possible. There should be no opportunity given 
for the finer particles of the material to work down and block 
the interstices of drain-pipes, etc. The half-acre beds which 
are being constructed in the Manchester scheme are provided 
with radial channels, all converging to the exit penstock. 
The channels will be covered with perforated tiles or cement 
blocks, and over these will be placed at least a foot of large 
lumps of clinker. 

(d) Solid Matter Entering Bed.—The decrease of capacity 
owing to solid inorganic matter entering the bed is not neces¬ 
sarily great, inasmuch as this material, especially if of a sandy 
nature, has itself a water-holding capacity. Its character will 
depend on the locality, i.e., whether the district is gravelly or 
clayey, etc. In any case the dry capacity of the bed will not 
be greatly affected. The danger is that the interstices of the 
bed may be filled up with clayey mud, which in the wet state 
will hold up the water and so decrease the wet or working 
capacity. This loss of capacity will not be affected by resting, 
and therefore all such solid matter should be retained, as far 
as possible, on the surface of the bed, and removed from time 
to time. It will be found to constitute excellent soil, as it will 


APPENDIX III. 


441 


contain nitrates and phosphates from the sewage, and cabbages 
and other vegetables will grow upon it. 

{/) Breaking Down of Material.—A more serious cause of 
loss of capacity than any of the foregoing is the disintegration 
of the material of the bed. This should be avoided at all costs 
by using only hard refractory material. When clinkers are 
used, as will probably be most commonly the case, such only 
as are hard and well fused should be put into the bed. All 
shale and ashes must be rejected. As a matter of fact, the 
ordinary weathering which an old cinder tip undergoes will 
generally have resulted in the disintegration of all but the 
harder portions. On screening, therefore, the fines will retain 
most of the softer material. 

To summarize the foregoing: for the successful working of 
bacteria beds the following method of procedure will be calcu¬ 
lated to give the best results: 

The bed must be worked very slowly at first, in order to 
allow it to settle down and the bacterial growths to form. In 
this way there will be less danger of suspended matter finding 
its way into the body of the bed while the material is still loose 
and open. 

The burden should not be increased till analysis reveals the 
presence of surplus oxygen, either dissolved, or in the form of 
nitrates, in the effluent. 

Analyses of the air in the bed may usefully be made from 
time to time during resting periods. 

Also the variations in the capacity should be carefully 
recorded. If the capacity is found to be rapidly decreasing a 
period of rest should be allowed. 

Long periods of rest should be avoided during winter, as, 
when deprived of the heat of the sewage, the activity of the 
organisms decreases. If necessary, the burden of the bed 
should then be decreased by reducing the number of fillings 
per day, rather than by giving a long rest at one time. 


442 


SE WEEA GE. 


The suspended matter may be retained on the surface by 
covering the latter with a layer of finer material not more than 
3 inches in depth. This should not be raked into the bed, but 
when the amount of suspended matter retained becomes exces¬ 
sive, it should be scraped off. This suspended matter may be 
tipped and made use of for agricultural purposes. 

By placing the inlet and outlet penstocks as close together 
as possible, the suspended matters will tend to concentrate at 
this point, and their removal will be facilitated. 

After many years it may, in spite of all precaution, be 
necessary to wash a portion, at any rate, of the material. It 
should not be difficult to devise a machine by which this may 
be easily and cheaply done, purified effluent water from a 
neighboring bed being used for the purpose. The mud so 
washed out will readily dry and may be also used for raising 
vegetables. 


INDEX. 


PAGE 

Acceptance of a system, Requirements for. 215 

Adams Sewage-lift. 152 

Advertising contracts. 239 

Aeration of filters.401, 428 

Aerobic bacteria, Definition of. 398 

Air, sewer, Character of.96, 99 

Albuminoid ammonia, Definition of.369, 376 

Alignment, Giving trench....... 244 

Alleys, Sewers in. 118 

Ammonia, Formation of, in sewage.369, 399 

Anaerobic bacteria, Definition of. 398 

Analyses, Chemical. 368 

Angles and bends in sewers.72, 119 

Arches, Providing for thrust of.298, 308 

Assessments, Conditions governing.233, 236 

, Methods of making. 231 

Atlantic City, Gaugings of sewage flow at. 39 

Back-filling, Cost of tamping. 212 

“ , Laborers used for. 268 

“ “ , Specifications for. 212 

Bacteria beds.402, 419 

“ in sewage, Effect of.367, 374 , 375 , 379 , 397 , 419 

Barrel, sewer, Shape of.81, 158 

Beginning construction, Points for. 241 

Bends in sewer lines. 72, ng 

Benefits derived from sewerage.1, 2, 18, 139, 236 

Berber system of sewerage. 7 

Bids, Receiving and considering. 239 

Blacksmith, Necessity for, during construction. 266 

Boxings, Test, along sewer lines. 109 

Boulders, Removing, from trench. 274 

Braces, Extensible. 287 

“ , Measuring trench for. 287 

Branches, Laying sewer.209, 242, 251, 296, 341 

443 





































444 


INDEX . 


PAGE 

Brick for sewers, Cost of. 227 

“ , Specifications for. 195 

Brick sewers, Abrasion of. 77 

“ , Centre for. 3 00 

, Cost of construction. 230 

“ “ in quicksand. 3 22 

“ “ , Invert backing for.297, 304 

“ “ , Method of building..299, 316 

“ “ , Templet for. 248, 298 

Bridging trenches, Specifications for. 201 

Broad irrigation, Cost of. 417 

, Crops grown by. 4 J o 

, Definition of. 407 

, Methods used in. 408 

Burlington, Vt., Gaugings of sewage flow at. 40 

C, Effect of variations in R upon.62, 71 

“, Meaning of. 61 

“, value of, Formulas for the. 62 

Canals, Crossing under. 337 

Capacity, Designing for future. 113 

Catch-basins, Cleaning.147, 348, 354 

, Construction of.•. 181 

, Where to use.146, 348, 431 

Caving of banks. Avoiding.273, 279 

Cement, Cost of. 231 

pipe-joints, Cost of. 228 

sewer-pipe, Use of.158, 170 

“ , Specifications for. 194 

, Specifications for. 197 

Centre for brick sewers. 302 

Cesspools . 3 

Chemical analyses. 368 

“ precipitation. See Precipitation. 

Chemistry of sewage.366, 369 

Chezy formula. 61 

Chlorine in sewage.363, 366, 370, 376 

Circular sewers, Conditions favoring use of. 81 

Clarification, Definition of. 377 

“ , Methods of. 377 

Cleaning large sewers.356 360 

sewers, Cost of. 360 

small sewers.264, 326, 355 

up streets, Specifications for. 215 

Coffer-dams, Construction of. 332 

Combined system defined. g 

vs. separate. I0 

Composition of sewage.361, 371 
















































INDEX. 


445 


PAG'? 

Concrete sewers. 163 

, Method of constructing. 304 

“ , Specifications for. 203 

Consumption of water, Daily and hourly variation in. 33 

, Estimating future. 33 

, per capita, Table of. 32 

Contact Filters.402, 419, 427, 437 

Contract, Form of. 223 

Contracting work, Advantages and disadvantages of. 237 

Contractor, Duties of. 220 

Contracts, Advertising. 239 

, Awarding. 240 

Cost, Relative, of sewers of different capacities. 57 

“ . See material or work in question. 

Cremation of sewage.6, 393 

Cross-section of sewer, Effect of shape of, upon velocity.69, 81 

Cultivation filters.403 

Curves, Loss of head in. 72 

Cutting sewer-pipe. 297 

Dead-ends in sewers.:. 119 

Defective sewers, Contractor’s responsibility for.215, 217 

Delays of construction, Provision in contract for. 217 

Depth of sewage, Minimum permissible.77, 83 

“ sewer desirable.132, 148 

“ “ , Relation of Q, S, and d to. 131 

Design, Data necessary for the.103, 106 

, Principles of sewerage.in, 136 

Des Moines, Gauging of sewage flow at. 41 

Dilution, Amount of, necessary in potable water.26, 374 


to prevent nuisance.19, 24, 26, 29, 375 


, Disposal by.14, 404 

“ “ “ , Conditions affecting.15, 19, 23, 28, 374, 404 

“ in tidal waters, Requirements for.5, 108, 114, 334 

Discharge into rivers and tidal waters. See Dilution. 

“ through circular sewers, Effect of depth upon. 69 

“ “ egg-shaped sewers, Effect of depth upon. 70 

“ “ sewers, Table of. 64 

“ “ “ partly full, Calculating the. 71 

Disk for cleaning small sewers. 357 

Disposal, Aims of. 16 

“ , Commercial aspect of. 17 

defined. 14 

“ , Laws affecting.12, 16, 19 

“ , Principles involved in. 18 

Drainage area, Ascertaining size of.103, 106 

“ “ , Data necessary concerning. 104 

“ districts. 117 














































446 


INDEX. 


t AGB 


« 


(« 


«( 


Drainage of wet soils. I 39 > 3 i 5 > 3 U 

Draining Trenches. See Water, Ground. 

Driving-cap for sheathing. 285 

Dry-sewage methods. 2 

Dwelling, Average number of persons in a. 35 

Earth-closet system. 5 

Egg-shaped sewers, Proportional dimensions of. 83 

“ “ “ , Advantages of, over circular.. 83 

Electricity for treating sewage, Use of.382, 386 

Engineer, Power of, in contract work. 220 

Engineer’s duties before construction. 241 

“ “ during “ . 254 

Estimate of cost, Data for making. 226 

Excavated materials, Classification of. 198 

“ “ , Placing of, on streets. 270 

Excavating deep trenches. 271, 279 

machinery, Advantages of using. 199, 249, 275, 290, 336 

, Different kinds of... 276 

“ , Economy of. 278 

trenches by hand. 270 

“ , Cost of. 229,315 

“ , Specifications for. 198 

Excreta,-Amount of per capita.361, 366 

Extra work, Specifications for. 218 

Factories, Amount of sewage from. 35 

Family, Average number of persons in a. 35 

Field-book, Form of notes in. 250,259 

Filtration beds, Maintenance of. 415 

, Cost of. 418 

, Definition of. 408 

, Efficiency of. 413 

“ , Methods used in. 412 

, Theory of. 400 

Final estimate book, Method of keeping. 257 

, Definition of. 256 

, Preparing.260 

inspection.215, 260 

Fish, Effect of sewage upon.22, 23, 24 

Flat-bottom sewers. 161 

Floats, Use of. 108 

Flow in sewers, Theory of. 60 

Flushing, Appliances for. 93, i 7 g y 349 

by hand, Methods of. 91, 350 

“, Relative cost of different. 353 

“ “ vs. automatic flushing. 353 

“ roof-water. 92 

, Efficiency of. go 

from streams and tide-waters. 92 


U 


ii 

















































INDEX. 


447 


PACK 

Flushing from water-mains direct. 95, 350 

, Intervals between.86 

, Necessity for.85, 97, 347 

, Proper methods of. 88 

, Sea-water for. 93 

, Separate sewers without. 90 

water, Amount of, necessary. 87 

Flush-tanks, Amount of water from. 37, 94 

, Automatic apparatus for. 93, 179, 349 

, Construction of.178,211,308,350 

“ , Inspection of. 349 

, Locating.145, 347 

, Method of building. 308 

“ , Specifications for. 211 

“ , Testing. 261 

Foremen, Number and character of. 266 

Foundations, Forms of. 298, 309 

, Materials for. 310 

, Specifications for. 202 

, Where needed. 189 

Free ammonia, Definition of. 369 

Gangs, labor, Size and number of. 265,267 

Gorged sewers, Relieving. 153, 185 

Grade cord, Setting and using. 245, 246 

rod, Form and use of. 248 

stakes, Use of. 245,250 

Grades of combined sewers. 76 

“ “ house-sewers. 75 134 

“ sewers, Calculating. 134 

“ “ , Desirable. 134 

“ “ “ , Maximum. 77 

“ storm-sewers. 76, 134 

Ground-water. See Water, Ground. 

Hose for cleaning small sewers. 264,326 

House-connections, Capacity of four-inch. 342 

“ “ , Interference of storm-sewers with. 137 

“ “ , Junction of, with sewers. 142 

“ “ , Line and grade of. 142 

“ “ , Locating.'. 242, 251 

“ “ , Method of cleaning. 359 

“ “ , Necessity of careful construction of. 100,141,340 

“ “ , Regulations for. 341, 346,349 

“ “ , Sewer-air in. 96 

“ “ , Size of. 79,342 

“ “ , Ventilating sewers through. 100,344 

“ “ with deep sewers. 188 

sewage, Amount of. 3 1 , H 3 , 120 
















































448 


INDEX. 


PAGE 

House sewage, Gaugings of. 37 

Hydraulic radius, Definition of. 61 

“ “ , Formula for, in circular sewers. 75 

“ “ , Tables of. 69 

Ice, Danger in sewage-polluted. 28 

Imperfect work, Contractor to repair. 217 

Imperviousness of ground and run-off. 51, 124 

“ “ “ , Determining ...... 124 

Injuries, Responsibility of contractor for. 217 

Inlet connections. 143, 181 

“ , Ventilating sewers through. 100,421 

Inlets, Construction of. 180, 308 

“ , Locating. 112, 145 

“ , Specifications for. 211 

Inspecting sewers. 260 

Inspection-hole. 342 

Inspection of house-drainage. 346, 349 

“ sewers, Necessity for.252, 347 

Inspector, Duties of. 252,255 

Intersections of sewers. 165, 215 

Intercepting-sewers . 116, 153 

Interceptors. 154 

, Leaping weir. 183 

, Diverting. 183 

Invert backing. 297, 304 

blocks. 163 

“ , Definition of. 245 

former for small sewers. 263 

Inverted siphons, Construction of. 186 

, “ “ , Principles of design of. 138, 185 

, Where used. 81, 132, 251, 329 

Inverts for brick sewers. 164 

Iron castings, Specifications for. 195 

“ , wrought, “ “. 196 

Irrigation. See Broad Irrigation. 

Joint-packing, Specifications for. 197 

Joints, Pipe-sewer. 118,168,204,319,329 

“ , Concrete around. 295, 319 

“ , Ward flexible, Cost of laying. 334 

Kalamazoo, Gaugings of sewage flow at. 40 

Kuichling’s laws of run-off. 48 

Kutter’s formula. 62 

Laborers, Housing non-resident. 269 

Lamp-holes, Construction of. 178 

“ , Where used. 145,251 

Laying sewer-pipe, Cost of. 229 

“ , Specifications for. 206 





















































INDEX. 


449 


PACK 


Leaks in sewers, Stopping. 206,261,319 

Legal status of stream pollution. 20 

Levelling necessary for designing. 105,107,242 

Liernur system of sewerage. 7 

Lifting sewage, Methods and apparatus for. 149, 150 

“ , When necessary. 148 

“ stations, Location of. 152 

“ , Number of, desirable. 150 

Lines, Locating sewer. 117,244 

Manhole bottoms. 176, 306 

buckets . 178 

steps . 172, 307 

tops . 177, 249,307 

walls . 177, 306 

Manholes, Building, in quicksand. 327 

, Cost of. 230 

, Crossing . 174 

, Dimensions of. 172 

, Drop . 174 

, Location of. 144, 171, 336 

, Materials and shapes of. 306 

, Method of building. 306 

on large sewers. 176 

, Purposes of. 100, 144 

, Shallow . 172,308 

, Specifications for. 210 

, Sub-drain . I 74 > 3 2 7 

Manufacturing wastes in sewage. 362 

“ “ , Removing, from sewage. 386 

Map required for designing. 103, 107 

Masonry, brick, Specifications for. 205 

“ sewers, Materials and shapes of. 297 

“ , stone block, Specifications for. 206 

“ stone, Specifications for. 204 

“ work in winter. 296,308 

Masons, Number of, required. 267 

Materials of sewer construction. (See also material or appurtenances 

in question.). I S 7 » 161 

Maul for driving sheathing. 285 

Measurement of work. 220, 256 

Memphis, Gaugings of sewage flow at. 40 

Mineralization, Definition of. 397 

“ , Methods of effecting.400 

Mirrors for inspecting sewers. 262 

Monthly estimates, Preparing. 258 

Mortar, Method of making. 204, 300 

and brick, Handling. 300 


« 


















































450 


INDEX. 


n in Kutter’s formula, Values for. 

Nitrates, Definition of. 

Nitrification, Definition of. 

“ . See Mineralization. 

Nitrites, Definition of. 

Nitrogen in sewage, Forms taken by.... 

Notes of the work. 

Nuisance, Dilution necessary to prevent. 

Object of a sewerage system. 

Obstructions, Causes of, in sewers. 

“ , Passing, by siphon. 

Office buildings, Amount of sewage from 

Old sewers, Using, in new system. 

Outlet, Deer Island, Cost of. 

Outlets for sewerage systems. 

, Construction of. 

Overflows . 

Oxidation of sewage, Desirability of. 

“ “ “ , Effect of. 

Oysters, Typhoid fever germs in. 

Packing, joint, Specifications for. 

Pail for earth-closet or pail system. 

Pail system. 

Paving, restoring, Specifications for. 

Payments, Times of making. 

Picks . 

Piles, Methods of driving. 

Pills, Use of, in cleaning sewers. 

Pipe, broken, Replacing, in sewers. 

“ , cement, Specifications for. 

“ , “ vs. vitrified clay. 

“ , drain, Specifications for. 

“ , “ , Cost of. 

“ , heavy, Methods of laying. 

“ , House-drain . 

“ , iron, Cost of. 

layers, Number of, required. 

“ , sewer, Cutting. 

“ , “ , Price of. 

“ , “ , Strength of. 

“ , “ , Thickness of. 

sewers, Cleaning. 

, Cost of laying. 

, Imperfections common in. 

in quicksand. 

». “ “ “ wet trenches. 


PAGE 

. 63 

. 370 , 376 

. 399 

. 370 

. 367,370 

. 250,255,257,258 

...19, 26, 406 

. 30 

. 85 

. 251 

. 35 

. 155 

. 333 

26, 28, 105, 108, 133, 148, 153 , 334 
. 333 

. 185 

. 397 

.369, 398 

. 23 

. 197 

. 5 

. 4 

. 214 

. 223, 269 

. 273 

. 309 

. 264,355 

. 34 T 359 

. 194 

. 170 

. 194 

. 228 

. 292 

. 345 

. 228 

. 267 

. 297 

. 227 

. 167 

. 166 

. 264, 325, 355 

. 229 

. 263 

. 322 

. 318, 325 















































INDEX . 


451 


PACK 

Pipe sewers, Inspecting. 254, 262 

, Laying, up or down hill. 291,317 

, Methods of laying. 291,319 

, Specifications for laying. 206 

“ , two-foot vs. three-foot lengths. 170 

“ , vitrified, Specifications for. 192 

Pipes and conduits, Interference with, by contractor. 200 

“ , Water, gas, or drain, in the trench. 274 

Plans, sewerage, Data required for. 103 

Platforms in deep trenches. 271 

Plumbing, Regulations for sanitary. 341 

Pneumatic systems. 7 

Pollution of streams, Effect of. 21 

Population, Distribution of, in families and dwellings. 34 

“ , Districts based on density of. 36, 116 

“ , Estimating future increase in. 35, 113 

“ per acre, Rule for calculating. 36 

Precipitation, Chemicals used for.380, 382, 385, 386 

, Cost of. 396 

“ , Effects of. 378 , 381,383 

“ , Methods employed in. 388 

“ tanks. 389 

Private property, Sewers on. 120 

Privies . .. .. 2 

Profiles, Information to be shown on.,. 131, 137 

“ necessary .. 105 

“ , Preparing. 107, 131 

Providence, Gaugings of sewage flow at. 38 

Pumping, hand, Methods of. 311,316 

“ , steam, “ “. 312 

“ . See Lifting. 

Pumps, Hand, on construction work. 311 

“ , Steam, on construction work. 312 

“ , sewage, Capacity of, necessary. 149 

“ , “ , Kinds of, in use. 151 

Purification by dilution.. x 4 , 404 

“ , Chemical changes during. 366 

“ , Extent of, necessary.27, 374 

Quicksand, Building brick sewers in. 249,322 

“ , “ manholes in. 327 

“ , “ pipe sewers in. 249,322 

“ , Detecting presence of. no 

“ , Handling trenches in.268, 317, 320, 322 

“ , Qualities of. 320 

“ , Removing, from pipe sewers. 325 

" , Sheathing in. 281, 283, 321 

R. See Hydraulic radius. 















































452 


INDEX. 


Raceways, Method of crossing under. 

Railroad crossings, Construction at. 

“ “ , Specifications for. 

Railroads, Sewers near. 

Rainfall, Rates of, in various sections. 

Ransome method of building sewers. 

Relief sewer, Purposes of. 

Removing a pipe from a sewer. 

Rivers, Methods of crossing. 

“ , Discharging sewage into. See Dilution. 

“ , Self-purification of. 

“ , Sewage-pollution of. 

Rock, Determining presence of. 

excavation, Cost of. 

“ “ , Measuring . 

“ “ , Sewers in. 

“ “ , Specifications for. 

Rods for cleaning small sewers. 

Run-off at Nagpoor reservoir. 

“ Washington, D. C. 

“ , Comparison of formulas for. 

conducted through gutters. 

“ , Diagrams for calculating. 

“ , Factors of. 

“ , Formulas for. 

“ , “ “ , Discussion of. 

“ , Gaugings of, at New Orleans. 

“ , Kuichling’s laws of. 

“ , Method of calculating. 

“ , Roe’s table for. 

S', Definition of. 

St. Louis, Gaugings of sewage flow at. 

Sand, Cost of. 

for mortar, Specifications for. 

Sanitary sewerage, Requirements of. 

Schenectady, Gaugings of sewage flow at. 

Sections of sewers. 

Sedimentation, Purification of sewage by. 

“ , “ “ streams “ . 


Separate system vs. combined... 

“ “ defined. 

Septic sewage, Definition of.... 

tank treatment.,. 

Sewage, Causes of danger from 

“ , Composition of. 

defined ., 

“ , Value of.. 


PAGE 

... 337 
... 335 
,.. 200 
... 336 
45 , 125 

... 305 
... 185 
. 34 i 
... 328 

24, 405 
. 19, 21 
... 109 
... 229 
.•. 257 
... 189 
... 201 
... 358 

... 51 
... 48 

• •. 55 

59, 112 
... 47 

• •• 44 

... 52 

• • • 54 

... 47 

... 48 
... 124 

... 54 

... 61 
... 40 
•.. 231 
... 196 


. 39 

. 158 

. 377 

.25, 405 

.. 10 

. 9 

.: 398 

13 , 403 , 423, 435 

■. 3, 18, 96 

. 15, 3i, 361 

. 15 

. 17 

















































INDEX. 


453 


PACK 

Sewage. See House- or Storm-sewage. 

Sewerage, Arguments in favor of. i, 2, 18, 139, 236 

Sewer-pipe. See Pipe, Sewer. 

Shape of sewer section. 81, 158 

Sheathers, Number of, necessary. 266,268 

Sheathing, Driving-cap and maul for. 282,285 

, Horizontal . 281,285 

, Materials and dimensions of. 284, 286 

, Removing . 289 

, Skeleton . 280,286 

trenches, Cost of. 229 

, Methods of. 280, 287, 321 

on steep slopes. 337 

Specifications for. 200 

, When necessary. 273, 2791 

, When to be left in. 288 

Shone Ejectors. 7, 152 

Shoring buildings. 200,29a 

Shovels . 273 

Sidewalks, Sewers under. 118 

Silt-basins, Use and construction of. 182 

Siphons, Inverted. See Inverted siphons. 

Sizes of house sewers, Method of determining. 31, 75, 78, 120 

“ “ “ “ , Minimum . 79 

“ sewers, Calculating, from sewage volume. 120, 134 

“ storm sewers, Method of determining. 44, 75, 122 

“ “ “ , Minimum . 80 

Sludge, Analyses of.... 394 

“ , Definition of. 388 

“ , Disposal of.393, 417 

Specifications, Classification of. 190* 

, Definition of. 190' 

, Requirements of. 191 

“ . See the material or work in question. 

Staging in trenches, Construction of. 271 

Steep slopes, Sheathing trenches on. 337 

Sterilizing sewage.375, 382, 387 

Stone, masonry, Specifications for. 195, 

, paving, 195. 

Stoneware sewer-pipe. See Pipe, Vitrified. 

Stores, Amount of sewage from. 35 

Storm overflows. 15 4 

sewage, Data for determining volume of. 122 

sewerage, Extent of. 112 

sewer, Determining size of. 57, 66, 80, 134 

“ water, Amount of, to be provided for. 56, 58 

Storms, Damage done by. 5? 












































454 


INDEX . 


) 


FAGS 


Storms, First, second, and third class. 56 

Street surfaces, Breaking, for trenches. 270 

“ “ , restoring, Specifications for... 214 

Sub-drain pipe, Specifications for.,.. . IQ4 

Sub-drains, Cleaning. 325 

“ “ , Construction of. 187 

for handling ground-water. 312, 317, 318 

*“ “ in quicksand. 324, 3^5 

“ , Inspecting. 264 

“ , Specifications for. 209 

“ , Necessity for. 139 

“ , Outlets for. 140 

“ “ , Size of. 141 

Sub-invert spaces. 189 

Surveys necessary for designing. 106 

System of sewerage, Which, to adopt. 12, 115, 149 

Tamping trenches, Cost of. 212 

“ “ , Methods of. 213, 295, 297 

, Specifications for. 213 

Tanks, Precipitation. 389 

Templet for sewers. 298 

“ , Inspector’s or skeleton. 262 

Tidal reservoirs. 148 

waters, Discharging sewage into. 28 

Timber, Specifications for. 197 

Time-keeper, Duties of. 266 

Toronto, Gaugings of sewage flow at. 39 

Traps, Location and use of. 97, 182, 343, 421 

Treatment, Sewage, Aims of.. 15, 374 

“ “ defined. 14 

“ “ , Difficulty of. 15 

, Method of, to be adopted.115, 429 

Trench machine. See Excavating machine. 

Trench, Storm- and house-sewer in the same. 120 

Trenches, Excavating. 270 

, Giving line for. 244, 270 

Tunnelling trenches. 272 

Typhoid-fever from polluted water. 22 

“ germs in oysters. 23 

Velocity in sewers, Effect of depth upon. 69 

“ , Formula for. 61 

“ “ “ , Table of. 64 

“ , Maximum, permissible. 77 

“ , Minimum, permissible in storm and combined sewers.... 74,76 

“ , “ £< “ house-sewers . 71,75 

“ , Uniform, in a system. 135 

Ventilation of sewers, Methods recommended for. 101,344,432 

















































INDEX . 


455 ' 

PAGE 

Ventilation of sewers, Necessity for. 95, 98 

“ , Various expedients for. 98 

Vitrified clay pipe. See Pipe, Vitrified. 

Walls, Thickness of sewer. 159, 165 

Water-carriage system. 7 

closet tanks. 344, 34s 

closets, Location of. 345, 

Water consumption and sewage flow. 31 

, Estimating future. 33, 114 

“ in various cities. 32 

“ , ground, Amount of, leaking into sewers.37, 169 

“ , “ , Detecting presence of. no 

“ , “ , Driven wells for lowering. 318. 

“ , “ , Handling .241, 310, 315, 318 

“ , “ , Sub-drains for handling. 312 

in trenches, Specifications governing. 199 

“ , Methods of constructing sewers under. 329 , 

“ , Tamping trenches with. 214 

Webster process of purification. 387 

Weston, W. Va., Gaugings of sewage flow at. 40 

Wet and quicksand trenches, Pipe-joints in. 319 

“ “ “ “ , Size of gangs for. 268 

“ “ “ “ . See Water, Ground. 

Winter, Masonry work in. 296, 308 

, Pipe-laying in. 308 

Wooden-stave pipe. 158 

Woolf process of treatment. 387 

Working gangs, Size and number of.266 





























— - : --- — *- 














I t* ► 

Engineering News. 

ESTABLISHED 1874. 

Pit. wished Every Thursday. Subscription, $5 a year. 


“Engineering News” makes a special feature of important original 
articles relating to Municipal and Civil Engineering. It aims to record 
everything of importance in all branches of American engineering practice, 
together with such foreign matters as are most likely to interest engineers 
in this country. 


The eight to twelve pages of Construction News items and Proposal 
Advertisements in “ Engineering News” are read each week by prominent 
contractors and manufacturers of contractors’ supplies in every part of 
North America, thus insuring an interest in work reported or advertised 
in this paper which often results in large savings on contracts. 


We also publish books on engineering and allied subjects. We have 
specifications for viaducts and bridges of various kinds, steel roofs and 
buildings, structural steel, grading and masonry, cross-ties, track-laying, 
dams and reservoirs, etc. There are some thirty different specifications, 
the price being from 5 to 40 cents each. The following books are of spe¬ 
cial interest to municipal engineers: 

PRICE. 


ENGINEERING CONTRACTS AND SPECIFICATIONS. By J. B. Johnson, Dean 
of the College of Mechanics and Engineering, University of Wisconsin. Cloth, 6x9 
inches, 452 pp. with index. $3 00 

MUNICIPAL YEAR BOOK. Giving wide range of information relating to all municipal¬ 
ities in the United States having a population of 3,000 or more By M. N. Baker, As¬ 
sociate Editor “ Engineering News.” Cloth, 6x9 inches, about 400 pp.3 00 

MANUAL OF AMERICAN WATER-WORKS. (1897 edition.) By M. N. Baker, As¬ 
sociate Editor “ Engineering News.” Cloth, 6x9 inches, 700 pp.3 00 


ECONOMICS OF ROAD CONSTRUCTION. By H. P. Gillette. Cloth, 6 x 9 inches, 

illustrated.,.. 00 

CITY ROADS AND PAVEMENTS. By W. P. Judson. (In press.) 

SEWAGE DISPOSAL IN THE UNITED STATES. By Geo. W. Rafter, M. Am. Soc. 

C. E., and M. N. Baker, Associate Editor “ Engineering News.” Cloth, 7 x 10 inches, 

598 pp.; 7 plates and 116 illustrations in the text.6 00 

ROAD MAKING AND MAINTENANCE. By Clemens Herschel. M. Am. Soc. C. E., 

and Edward P. North, M. Am. Soc. C. E. Paper, 6x9 inches, 156 pp. 5 ° 

Any Standard Books on Engineering and Allied Subjects may be procured 
from our New York and Chicago offices. 

A complete list of our own books or a sample copy of “Engineering News ” 

will be mailed on application. 


The Engineering News Publishing Co., 

Chicago Branch : 1636 Monadnock Block. Publication Office : 220 Broadway, New York. 














WORKS ON SEWAGE AND SEWERAGE. 

* . I w* i » & 

Sewage and the Bacterial Purification of Sewage. By Dr. Samuel Rideal. 

8vo, cloth, 47 illustrations.$3*5° 

Sewer Design. By H. N. Ogden, C.E., Assoc. M. Am. Soc. C. E., Assist¬ 
ant Professor of Civil Engineering, Cornell University, xi-l-234 pp., i2mo, 

cloth. $ 2.00 

Sewage Disposal. By Wynkoop Kiersted. i6mo, cloth... .*.. $1*25 

Sewerage. The Designing, Construction, and Maintenance of Sewerage Sys¬ 
tems. By A. Prescott Folwell'. 5th edition, revised. 8vo, x -j- 454 

pages, 13 full-page plates and 38 figures in the text, cloth.$3.00 

Sewage Works Analyses. By Gilbert J. Fowler, M.Sc. (Viet.), F.I.C., 
Superintendent and Chemist, Manchester Corporation Sewage Works. 
i2mo, vii —(— 135 pp., 11 figures, cloth.$2.00 

Order through, your bookseller , or copies will be forwarded postpaid by 
the publishers on the receipt of the retail price. 

JOHN WILEY & SON S, 43 & 45 e n1^ToKty h street ’ 

A. Prescott Folwell, m. Am. s oc . c. e., 

EASTON, PA., 

CONSULTING ENGINEER FOR SEWERAGE, DRAINAGE, WATER 
SUPPLY, AND GENERAL MUNICIPAL WORK. 


Designs furnished and Construction superintended. Reports on and Im¬ 
provements and Extensions of Existing Systems. 

THE MILLER AUTOMATIC SIPHON. 



Pacific Flush Tank Co., 


84 La Salle St., 


i 


Chicago, Ills. 
































I 







/ 




SHORT-TITLE CATALOGUE 

OF THE 

PUBLICATIONS 

OF 

JOHN WILEY & SONS, 

New York. 

London : CHAPMAN & HALL, Limited. 
ARRANGED UNDER SUBJECTS. 


sold at net prices only, a double asterisk (**) books sold under the rules of the 
American Publishers Association at net prices subject to an extra charge for 
Dostage. All books are bound in cloth unless otherwise stated. 


AGRICULTURE. 

Armsby’s Manual of Cattle-feeding.nmo, Si 75 

Principles of Animal Nutrition.8vo, 4,00 

Budd and Hansen’s American Horticultural Manual: 

Part I.—Propagation, Culture, and Improvement.i2mo, 1 50 

Part II.—Systematic Pomology.nmo, 1 50 

Downing’s Fruits and Fruit-trees of America.8vo, 5 00 

Elliott’s Engineering for Land Drainage.nmo, 1 50 

Practical Farm Drainage.nmo, 1 00 

Green’s Principles of American Forestry.nmo, 1 50 

Grotenfelt’s Principles of Modern Dairy Practice. (Woll.).nmo, 2 00 

Kemp’s Landscape Gardening.nmo, 2 50 

Maynard’s Landscape Gardening as Applied to Home Decoration.nmo, 1 50 

Sanderson’s Insects Injurious to Staple Crops.nmo, 1 50 

Insects Injurious to Garden Crops. (In preparation.) 

Insects Injuring Fruits. (In preparation.) 

Stockbridge’s Rocks and Soils.8vo, 2 50 

Woll’s Handbook for Farmers and Dairymen.ibmo, 1 50 

ARCHITECTURE. 

Baldwin’s Steam Heating for Buildings.i2mo, 2 50 

Berg’s Buildings and Structures of American Railroads.4to, 5 00 

Birkmire’s Planning and Construction of American Theatres. 8vo, 300 

Architectural Iron and Steel.8vo, 3 50 

Compound Riveted Girders as Applied in Buildings.8vo, 2 00 

Planning and Construction of High Office Buildings.8vo, 3 50 

Skeleton Construction in Buildings.8vo, 3 00 

Briggs’s Modern American School Buildings.8vo, 4 00 

Carpenter’s Heating and Ventilating of Buildings.8vo, 4 00 

Freitag’s Architectural Engineering. 2d Edition, Rewritten.8vo, 350 

Fireproofing of Steel Buildings.8vo, 2 50 

French and Ives’s Stereotomy.8vo, 2 50 

Gerhard’s Guide to Sanitary House-inspection.*i6mo, 1 co 

Theatre Fires and Panics.nmo, 1 50 

































Holly’s Carpenters’and Joiners’fiandb* ..*.i8mo, o 75 

Johnson’s Statics by Algebraic and Graphic Methods . 8vo 2 00 

Kidder’s Architect’s and Builder’s Pocket-book. (Rewritten edition in preparation.) 

Merrill’s Stones for Building and Decoration. 8vo, 5 00 

Monckton’s Stair-building.4to, 4 00 

Patton’s Practical Treatise on Foundations.8vo, 5 00 

Siebert and Biggin’s Modern Stone-cutting and Masonry.8vo, 1 50 

Snow’s Principal Species of Wood. ..8vo, 3 50 

Sondericker’s Graphic Statics with Applications to Trusses, Beams, and Arches. 

8vo, 2 00 

Wait’s Engineering and Architectural Jurisprudence.8vo, 6 00 

Sheep, 6 50 

Law of Operations Preliminary to Construction in Engineering and Archi¬ 
tecture.8vo, 5 00 

Sheep, 5 50 

Law of Contracts . 8vo, 3 00 

Woodbury’s Fire Protection of Mills.8vo, 2 50 

Worcester and Atkinson’s Small Hospitals, Establishment and Maintenance, 
Suggestions for Hospital Architecture, with Plans for a Small Hospital. 

i2mo, 1 25 

The World’s Columbian Exposition of 1893. Large 4to, 1 00 


ARMY AND NAVY. 


-Bernadou’s Smokeless Powder, Nitro-cellulose, and the Theory of the Cellulose 

Molecule.nmo, 2 50 

* Bruff’s Text-book Ordnance and Gunnery.8vo, 6 00 

Chase’s Screw Propellers and Marine Propulsion.8vo, 3 00 

Craig’s Azimuth.4to, 3 50 

Crehore and Squire’s Polarizing Photo-chronograph.8vo, 3 00 

■Cronkhite’s Gunnery for Non-commissioned Officers.24mo= morocco, 2 00 

* Davis’s Elements of Law. 8vo, 2 50 

* Treatise on the Military Law of United States. 8vo, 7 00 

Sheep, 7 50 

De Brack’s Cavalry Outpost Duties. (Carr.).241110 morocco, 2 00 

Dietz’s Soldier’s First Aid Handbook.i6mo, morocco, 1 25 

* Dredge’s Modern French Artillery.4to, half morocco, 15 00 

Durand’s Resistance and Propulsion of Ships.8vo, 5 00 

* Dyer’s Handbook of Light Artillery.i2mo, 3 00 

Eissler’s Modern High Explosives.8vo, 4 00 

’* Fiebeger’s Text-book on Field Fortification.Small 8vo, 2 00 

Hamilton’s The Gunner’s Catechism.i8mo, 1 00 

* Hoff’s Elementary Naval Tactics.8vo, 1 50 

Ingalls’s Handbook of Problems in Direct Fire.8vo, 4 00 

* Ballistic Tables.8vo, 1 50 

* Lyons’s Treatise on Electromagnetic Phenomena. Vols. I. and II. .8vo.each, 6 00 

♦Mahan’s Permanent Fortifications. (Mercur.).8vo, half morocco, 7 50 

Manual for Courts-martial.i6mo. morocco, 1 50 

* Mercur’s Attack of Fortified Places.nmo, 2 00 

* Elements of the Art of War.8vo, 4 00 

Metcalf’s Cost of Manufactures—And the Administration of Workshops, Public 

and Private.8vo, 5 00 

* Ordnance and Gunnery. 2 vols.nmo, 5 00 

Murray’s Infantry Drill Regulations.i8mo, paper, 10 

* Phelps’s Practical Marine Surveying.8vo, 2 50 

Powell’s Army Officer’s Examiner.nmo, 4 00 

SI arpe’s Art of Subsisting Armies in War.i8mo, morocco. 1 co 

2 











































* Walke’s Lectures on Explosives.ovo 4 00 

* Wheeler’s Siege Operations and Military Mining.8vo, 2 00 

Winthrop’s Abridgment of Military Law.121110, 2 50 

Woodhull’s Notes on Military Hygiene.i6mo, 1 50 

Young’s Simple Elements of Navigation.i6mo morocco, 1 00 

Second Edition, Enlarged and Revised.i6mo, morocco, 2 00 

ASSAYING. 

Fletcher’s Practical Instructions in Quantitative Assaying with the Blowpipe. 

i2mo, morocco, 1 50 

Furman’s Manual of Practical Assaying.8vo, 3 00 

Miller’s Manual of Assaying.nmo, 1 00 

O’Driscoll’s Notes on the Treatment of Gold Ores.8vo, 2 00 

Ricketts and Miller’s Notes on Assaying.8vo, 3 00 

Ulke’s Modern Electrolytic Copper Refining.8vo, 3 00 

Wilson’s Cyanide Processes.i2mo, 1 50 

Chlorination Process.nmo, 1 50 

ASTRONOMY. 

Comstock’s Field Astronomy for Engineers.8vo, 2 50 

Craig’s Azimuth. 4to, 3 50 

Doolittle’s Treatise on Practical Astronomy.8vo, 4 00 

Gore’s Elements of Geodesy.8vo, 2 50 

Hayford’s Text-book of Geodetic Astronomy.8vo, 3 00 

Merriman’s Elements of Precise Surveying and Geodesy.8vo, 2 50 

* Michie and Harlow’s Practical Astronomy.8vo, 3 00 

* White’s Elements of Theoretical and Descriptive Astronomy.nmo, 2 00 

BOTANY. 

Davenport’s Statistical Methods, with Special Reference to Biological Variation. 

i6mo, morocco, 1 25 

Thome and Bennett’s Structural and Physiological Botany.i6mo, 2 25 

Westermaier’s Compendium of General Botany. (Schneider.).8vo, 2 00 

CHEMISTRY. 

Adriance’s Laboratory Calculations and Specific Gravity Tables.nmo, t 25 

Allen’s Tables for Iron Analysis.8vo, 3 00 

Arnold’s Compendium of Chemistry. (Mandel.) (In preparation.) 

Austen’s Notes for Chemical Students.i2mo, 1 50 

Bernadou’s Smokeless Powder.—Nitro-cellulose, and Theory of the Cellulose 

Molecule. .i2mo, 2 30 

Bolton’s Quantitative Analysis.8vo, 1 50 

* Browning’s Introduction to the Rarer Elements.8vo, 1 50 

Brush and Penfield’s Manual of Determinative Mineralogy.8vo. 4 00 

Classen’s Quantitative Chemical Analysis by Electrolysis. (Boltwood.) . .. 8vo, 3 00 

Cohn’s Indicators and Test-papers.i2mo, 2 00 

Tests and Reagents.8vo, 3 00 

Copeland’s Manual of Bacteriology. (In preparation.) 

Craft’s Short Course in Qualitative Chemical Analysis. (Schaeffer.)-i2mo, 1 30 

Drechsel’s Chemical Reactions. (Merrill.).i2mo, 1 25 

Duhem’s Thermodynamics and Chemistry. (Burgess.).8vo, 400 

Eissler’s Modern High Explosives. -8vo, 4 °® 


3 







































Effront’s Enzymes and their Applications. (Prescott.).8vo, 3 00 

Erdmann’s Introduction to Chemical Preparations. (Dunlap.).nmo, 1 25 

Fletcher’s Practical Instructions in Quantitative Assaying with the Blowpipe 

nmo, morocco, 1 50 

Fowler’s Sewage Works Analyses.nmo, 2 00 

Fresenius’s Manual of Qualitative Chemical Analysis. (Wells.).8vo, 5 00 

Manual of Qualitative Chemical Analysis. Parti. Descriptive. (Wells.) 

8vo, 3 00 

System of Instruction in Quantitative Chemical Analysis. (Cohn.) 

2 vols. 


Grotenfelt’s Principles of Modern Dairy Practice. (Wo 
Hammarsten's Text-book of Physiological Chemistry. 
Helm’s Principles of Mathematical Chemistry. (Morgj 


Holleman’s Text-book of Inorganic Chemistry. 
Text-book of Organic Chemistry. (Walke 



12 

50 


1 

50 


3 

00 


1 

25 


2 

00 


4 

00 


1 

50 


3 

00 



75 


2 

50 


2 

50 


3 

00 

y.. 8 vo, 

1 

25 


2 

50 


I 

00 


3 

00 


1 

00 


Landauer’s Spectrum Analysis. (Tingle.)... 

Lassar-Cohn’s Practical Urinary Analysis. (Lorenz.). 

Leach’s The Inspection and Analysis of Food with Special Reference to State 
Control. ( 7 n 'preparation.) 

Lob’s Electrolysis and Electrosynthesis of Organic Compounds. (Lorenz.) nmo, 
Mandel’s Handbook for Bio-chemical Laboratory.‘.nmo, 

* Martin’s Laboratory Guide to Qualitative Analysis with the Blowpipe. . nmo, 
Mason’s Water-supply. (Considered Principally from a Sanitary Standpoint.) 

3d Edition, Rewritten.8vo, 

Examination of Water. (Chemical and Bacteriological.).nmo, 

Mayer’s Determination of Radicles in Carbon Compounds. (Tingle.). 

Miller’s Manual of Assaying.1 

Mixter’s Elementary Text-book of Chemistry.1 

Morgan’s Outline of Theory of Solution and its Results.nmo, 

Elements of Physical Chemistry.. 

Nichols’s Water-supply. (Considered mainly from a Chemical ar 

Standpoint, 1883.).8vo, 

O’Brine’s Laboratory Guide in Chemical Analysis.8vo, 

O’Driscoll’s Notes on the Treatment of Gold Ores.8vo, 

Ost and Kolbeck’s Text-book of Chemical Technology. (Lorenz—Bozart.) 
(In preparation.) 

* Penfield’s Notes on Determinative Mineralogy and Record of Mineral Tests. 

8vo, paper, 

Pictet’s The Alkaloids and their Chemical Constitution. (Biddle.) (In 
preparation.) 

Pinner’s Introduction to Organic Chemistry. (Austen.).i2mo, 

Poole’s Calorific Power of Fuels.8vo 

* Reisig's Guide to Piece-dyeing.8vo, 

Richards and Woodman’s Air .Water, and Food from a Sanitary Standpoint. 8vo, 
Richards’s Cost of Living as Modified by Sanitary Science.i2mo, 

Cost of Food a Study in Dietaries. i2mo, 

* Richards and Williams’s The Dietary Computer.8vo, 

Ricketts and Russell’s Skeleton Notes upon Inorganic Chemistry. (Part I.— 

Non-metallic Elements.).8vo, morocco. 


00 

so 

60 



4 

00 


1 

25 

. . nmo, 

1 

00 


1 

00 


1 

50 


1 

00 


2 

00 

sanitary 




2 

SO 


2 

00 


2 

00 


1 
3 

25 

2 
1 
1 
1 


50 


50 

00 

00 

00 

00 

00 

50 

75 


4 







































Ricketts and Miller’s Notes on Assaying.8vo, 3 00 

Rideal’s Sewage and the Bacterial Puritication of Sewage.8vo, 3 50 

Disinfection and the Preservation of Food.8vo, 4 00 

Ruddiman’s Incompatibilities in Prescriptions.8vo, 2 00 

Salkowski’s Physiological and Pathological Chemistry. (Orndorff.). . . .8vo, 2 50 

Schimpf’s Text-book of Volumetric Analysis.i2mo, 2 50 

Essentials of Volumetric Analysis. i2mo, 1 25 

Spencer’s Handbook for Chemists of Beet-sugar Houses.i6mo, morocco, 3 00 

Handbook for Sugar Manufacturers and their Chemists. . i6mo, morocco, 2 00 

Stockbridge s Rocks and Soils.. 8vo, 2 50 

* Tillman’s Elementary Lessons in Heat.8vo, 1 50 

* Descriptive General Chemistry.8vo 3 00 

Treadwell’s Qualitative Analysis. (Hall.).8vo, 3 00 

Turneaure and Russell’s Public Water-supplies.8vo, 5 00 

Van Deventer’s Physical Chemistry for Beginners. (Boltwood.).i2mo, 1 50 

* Walke’s Lectures on Explosives.8vo, 4 00 

Wells’s Laboratory Guide in Qualitative Chemical Analysis.8vo, 1 50 

Short Course in Inorganic Qualitative Chemical Analysis for Engineering 

Students.„.12 mo, 1 50 

Whipple’s Microscopy of Drinking-water..8vo, 3 50 

Wiechmann’s Sugar Analysis.Small 8vo. 2 50 

Wilson’s Cyanide Processes.nmo, 1 50 

Chlorination Process.i2mo 1 50 

Wulling’s Elementary Course in Inorganic Pharmaceutical and Medical Chem¬ 
istry.i2mo 2 00 

CIVIL ENGINEERING. 

BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF ENGINEERING 

RAILWAY ENGINEERING. 

Baker’s Engineers’Surveying Instruments.i2mo, 3 00 

Bixby’s Graphical Computing Table.Paper 19^X24^ inches. 25 

** Burr’s Ancient and Modern Engineering and the Isthmian Canal. (Postage, 

27 cents additional.).8vo, net, 3 50 

Comstock’s Field Astronomy for Engineers.8vo, 2 50 

Davis’s Elevation and Stadia Tables.'. ...8vo, 1 00 

Elliott’s Engineering for Land Drainage.i2mo, 1 50 

Practical Farm Drainage.i2mo, 1 00 

Folwell’s Sewerage. (Designing and Maintenance.).8vo, 3 00 

Freitag’s Architectural Engineering. 2d Edition, Rewritten.8vo, 350 

French and Ives’s Stereotomy.8vo, 2 50 

Goodhue’s Municipal Improvements.i2mo, 1 75 

Goodrich’s Economic Disposal of Towns’Refuse.8vo, 3 50 

Gore’s Elements of Geodesy.8vo, 2 so 

Hayford’s Text-book of Geodetic Astronomy.8vo, 3 00 

Howe’s Retaining Walls for Earth.i2mo, 1 25 

Johnson’s Theory and Practice of Surveying.Small 8vo, 4 00 

Statics by Algebraic and Graphic Methods.8vo, 2 00 

Kiersted’s Sewage Disposal.i2mo, 1 25 

Laplace’s Philosophical Essay on Probabilities. (Truscott and Emory.) i2mo, 2 00 

Mahan’s Treatise on Civil Engineering. (1873.) (Wood.).8vo, 500 

* Descriptive Geometry.8vo, 1 50 

Merriman’s Elements of Precise Surveying and Geodesy.8vo, 2 50 

Elements of Sanitary Engineering.8vo, 2 00 

Merriman and Brooks’s Handbook for Surveyors.i6mo, morocco, 2 00 

Nugent’s Plane Surveying.8vo, 350 

Ogden’s Sewer Design.i2mo, 2 00 

Patton’s Treatise on Civil Engineering.8vo half leather, 7 50 


5 


















































Reed’s Topographical Drawing and Sketching.4to 

Rideal’s Sewage and the Bacterial Purification of Sewage.8vo, 

Siebert and B’ggin’s Modern Stone-cutting and Masonry.8vo, 

Smith’s Manual of Topographical Drawing. (McMillan.).8vo, 

Sondericker’s Graphic Statics, wun Applications to Trusses, Beams, and 
Arches.8vo, 

* Trautwine’s Civil Engineer’s Pocket-book.i6mo, morocco. 

Wait’s Engineering and Architectural Jurisprudence.8vo, 

Sheep, 

Law of Operations Preliminary to Construction in Engineering and Archi¬ 
tecture .8vo. 

Sheep 

Law of Contracts.8vo, 

Warren’s Stereotomy—Problems in Stone-cutting.8vo, 

Webb’s Problems in the U c e and Adjustment of Engineering Instruments. 

i6mo, morocco, 

* Wheeler’s Elementary Course of Civil Engineering.8vo, 

Wilson’s Topographic Surveying.8vo. 


5 oo 
3 50 

1 50 

2 50 

2 00 

5 00 

6 00 
6 50 

5 00 
5 SO 

3 00 

2 50 

1 25 

4 00 

3 50 


BRIDGES AND ROOFS. 

Boiler’s Practical Treatise on the Construction of Iron Highway Bridges. .8vo, 2 00 


* Thames River Bridge.4to, paper, 5 00 

Burr's Course on the Stresses in Bridges and Roof Trusses, Arched Ribs, and 

Suspension Bridges.8vo, 3 50 

Du Bois’s Mechanics of Engineering. Vol. II.Small 4to, 10 00 

Foster’s Treatise on Wooden Trestle Bridges.4to, 5 00 

Fowler’s Coffer-dam Process for Piers.8vo, 2 50 

Greene’s Roof Trusses.8vo, 1 25 

Bridge Trusses.. 8vo, 2 so 

Arches in Wood, Iron, and Stone.8vo, 2 50 

Howe’s Treatise on Arches.8vo 4 00 

Design of Simple Roof-trusses in Wood and Steel.8vo, 2 00 . 

Johnson. Bryan, and Turneaure’s Theory and Practice in the Designing of 

Modern Framed Structures.Small 4to, 10 00 

Merriman and Jacoby’s Text-book on Roofs and Bridges: 

Parti.—Stresses in Simple Trusses...8vo, 2 50 

Part II.—Graphic Statics..8vo, 2 50 

Part III.—Bridge Design. 4th Edition, Rewritten.8vo, 2 50 

Part IV.—Higher Structures.8vo, 2 50 

Morison’s Memphis Bridge.4to, 1000 

Waddell’s De Pontibus, a Pocket-book for Bridge Engineers.. . i6mo, morocco, 3 00 

Specifications for Steel Bridges.i2mo, 1 25 

Wood’s Treatise on the Theory of the Construction of Bridges and Roofs.8vo, 2 00 
Wright’s Designing of Draw-spans: 

Part I. —Plate-girder Draws...8vo, 2 50 

Part II.—Riveted-truss and Pin-connected Long-span Draws.8vo, 2 50 

Two parts in one volume.8vo, 3 50 


HYDRAULICS. 

Bazin’s Experiments upon the Contraction of the Liquid Vein Issuing from an 


Orifice. (Trautwine.).8vo, 2 00 

Bovey’s Treatise on Hydraulics.8vo, 5 00 

Church’s Mechanics of Engineering.8vo, 6 00 

Diagrams of Mean Velocity of Water in Open Channels..paper, x 50 

6 






































Coffin’s Graphical Solution of Hydraulic Problems.i6mo, morocco, 2 50 

Flather’s Dynamometers, and the Measurement of Power.i2mo, 3 00 

Folwell’s Water-supply Engineering.8vo, 4 00 

Frizell’s Water-power.8vo, 5 00 

Fuertes’s Water and Public Health.nmo, 1 50 

Water-filtration Works.i2mo, 2 50 

Ganguillet and Kutter’s General Formula for the Uniform Flow of Water in 

Rivers and Other Channels. (Hering and Trautwine.).8vo, 4 00 

Hazen’s Filtration of Public Water-supply.8vo, 3 00 

Hazlehurst’s Towers and Tanks for Water-works.8vo, 2 50 

Herschel’s 115 Experiments on the Carrying Capacity of Large, Riveted, Metal 

Conduits.8vo, 2 00 

Mason’s Water-supply. (Considered Principally from a Sanitary Stand¬ 
point.) 3d Edition, Rewritten.8vo, 4 00 

Merriman’s Treatise on Hydraulics, gth Edition, Rewritten.8vo, 5 00 

* Michie’s Elements of Analytical Mechanics.8vo, 4 00 

Schuyler’s Reservoirs for Irrigation, Water-power, and Domestic Water- 

supply.Large 8vo, 5 00 

** Thomas .and Watt's Improvement of Riyers. (Post., 44 c. additional), 4to, 6 00 

Turneaure and Russell’s Public Water-supplies.8vo, 5 00 

Wegmann’s Desien and Construction of Dams.4to, 5 00 

Water-supply of the City of New York from 1658 to Y8 q5 .4to, 10 00 

Weisbach’s Hydraulics and Hydraulic Motors. (Du Bois.).8vo, 5 00 

Wilson’s Manual of Irrigation Engineering.Small 8vo. 4 00 

Wolff’s Windmill as a Prime Mover.8vo, 3 00 

Wood’s Turbines.8vo, 2 50 

Elements of Analytical Mechanics.8vo, 3 oc 

MATERIALS OF ENGINEERING. 

Baker’s Treatise on Masonry Construction.8vo, 5 00 

Roads and Pavements.8vo, 5 00 

Black’s United States Public Works.oblong 4to, 5 00 

Bovey’s Strength of Materials and Theory of Structures.8vo, 7 50 

Burr’s Elasticity and Resistance of the Materials of Engineering. 6th Edi¬ 
tion, Rewritten.8vo, 7 50 

Byrne’s Highway Construction.8vo, 5 00 

Inspection of the Materials and Workmanship Employed in Construction. 

i6mo, 3 00 

Church’s Mechanics of Engineering.8vo, 6 00 

Du Bois’s Mechanics of Engineering. Vol. I.Small 4to, 7 50 

Johnson’s Materials of Construction.Large 8vo, 6 00 

Keep’s Cast Iron.8vo, 2 50 

Lanza’s Applied Mechanics. . 8 vo, 7 50 

Martens’s Handbook on Testing Materials. (Henning.) 2 vols.8vo, 7 5 o 

Merrill’s Stones for Building and Decoration.8vo, 5 00 

Merriman’s Text-book on the Mechanics of Materials.8vo, 4 00 

Strength of Materials.nmo, 1 00 

Metcalf’s Steel. A Manual for Steel-users.nmo, 2 00 

Patton’s Practical Treatise on Foundations.8vo, 5 00 

Rockwell’s Roads and Pavements in France.nmo, 1 25 

Smith’s Materials of Machines.nmo, 1 00 

Snow’s Principal Species of Wood.8vo, 3 50 

Spalding’s Hydraulic Cement.nmo, 2 00 

Text-book on Roads and Pavements.nmo, 2 00 


7 















































Thurston’s Materials of Engineering. 3 Parts. 8vo, 8 00 

Part I.—Non-metallic Materials of Engineering and Metallurgy.8vo, 2 00 

Part II.—Iron and Steel.8vo, 3 50 

Part III.—A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents.8yo, 2 50 

Thurston’s Text-book of the Materials of Construction.8vo, 5 00 

Tillson’s Street Pavements and Paving Materials.8vo, 4 00 

Waddell’s De Pontibus. (A Pocket-book for Bridge Engineers.).. i6mo, mor., 3 00 

Specifications for Steel Bridges.i2mo, 1 25 

Wood’s Treatise on the Resistance of Materials, and an Appendix on the Pres¬ 
ervation of Timber.8vo, 2 00 

Elements of Analytical Mechanics.8vo, 3 00 

Wood’s Rustless Coatings. (Shortly.) 

RAILWAY ENGINEERING. 

Andrews’s Handbook for Street Railway Engineers. 3X5 inches, morocco, 1 25 

Berg’s Buildings and Structures of American Railroads.4to, 5 00 

Brooks’s Handbook of Street Railroad Location.i6mo. morocco, 1 50 

Butts’s Civil Engineer’s Field-book.i6mo, morocco, 2 50 

Crandall’s Transition Curve.i6mo, morocco, 1 50 

Railway and Other Earthwork Tables.8vo, 1 50 

Dawson’s “Engineering” and Electric Traction Pocket-book. i 6 mo, morocco, 5 00 

Dredge’s History of the Pennsylvania Railroad: (1879).Paper, 5 00 

* Drinker’s Tunneling, Explosive Compounds, and Rock Drills, 4to, half mor., 25 00 

Fisher’s Table of Cubic Yards.Cardboard 25 

Godwin’s Railroad Engineers* Field-book and Explorers’ Guide.i6mo, mor., 2 50 

Howard’s Transition Curve Field-book. i6mo, morocco. 1 50 

Hudson’s Tables for Calculating the Cubic Contents of Excavations and Em¬ 
bankments .. 8vo, 1 00 

Molitor and Beard’s Manual for Resident Engineers.i6mo, 1 00 

Nagle’s Field Manual for Railroad Engineers.i6mo, morocco. 3 00 

Philbrick’s Field Manual for Engineers.i6mo, morocco, 3 00 

Pratt and Alden’s Street-railway Road-bed.8vo, 2 00 

Searles’s Field Engineering.i6mo, morocco, 3 00 

Railroad Spiral.i6mo, morocco, 1 50 

Taylor’s Prismoidal Formulae and Earthwork.8vo, 1 50 

* Trautwine’s Method of Calculating the Cubic Contents of Excavations and 

Embankments by the Aid of Diagrams.8vo, 2 00 

The Field Practice of [Laying Out Circular Curves for Railroads. 

i2mo, morocco, 2 50 

* Cross-section Sheet.Paper, 25 

Webb’s Railroad Construction. 2d Edition, Rewritten.i6mo. morocco, 5 00 

Wellington’s Economic Theory of the Location of Railways.Small 8vo, 5 00 

DRAWING. 

Barr’s Kinematics of Machinery.8vo, 2 50 

* Bartlett’s Mechanical Drawing.8vo, 3 00 

* 4 “ Abridged Ed.8vo, 1 50 

Coolidge’s Manual of Drawing...8vo, paper, 1 00 

Durley’s Kinematics of Machines.8vo, 4 00 

Hill’s Text-book on Shades and Shadows, and Perspective.8vo, 2 00 

Jones’s Machine Design: 

Part I.—Kinematics of Machinery..8vo, 1 50 

Part II.—Form, Strength, and Proportions of Parts.8vo 3 00 

8 








































MacCord’s Elements of Descriptive Geometry.8vo, 3 

Kinematics; or, Practical Mechanism.8vo, 5 

Mechanical Drawing.4to, 4 

Velocity Diagrams.8vo, 1 

* Mahan’s Descriptive Geometry and Stone-cutting.8vo, 1 

Industrial Drawing. (Thompson.).8vo, 3 

Reed’s Topographical Drawing and Sketching .4to, 5 

Reid’s Course in Mechanical Drawing.8vo, 2 

Text-book of Mechanical Drawing and Elementary Machine Design. .8vo, 3 

Robinson’s Principles of Mechanism.8vo, 3 

Smith’s Manual of Topographical Drawing. (McMillan.).8vo, 2 

Warren’s Elements of Plane and Solid Free-hand Geometrical Drawing.. i2mo, 1 

Drafting Instruments and Operations.i2mo, 1 

Manual of Elementary Projection Drawing.i2mo, 1 

Manual of Elementary Problems in the Linear Perspective of Form and 

Shadow.i2mo, 1 

Plane Problems in Elementary Geometry.i2mo, 1 

Primary Geometry.nmo, 

Elements of Descriptive Geometry, Shadows, and Perspective.8vo, 3 

General Problems of Shades and Shadows. 8 vo, 3 

Elements of Machine Construction and Drawing. 8 vo, 7 

Problems. Theorems, and Examples in Descriptive Geometry.8vo, 2 

Weisbach’s Kinematics and the Power of Transmission. vHermann and 

Klein.) . . 8vo, 5 

Whelpley’s Practical Instruction in the Art of Letter Engraving.nmo, 2 

Wilson’s Topographic Surveying.8vo, 3 

Free-hand Perspective.8vo, 2 

Free-hand Lettering.8vo, 1 

Woolf’s Elementary Course in Descriptive Geometry.Large 8vo, 3 

ELECTRICITY AND PHYSICS. 

Anthony and Brackett’s Text-book of Physics. (Magie.).Small 8vo, 3 

Anthony’s Lecture-notes on the Theory of Electrical Measurements.12mo, 1 

Benjamin’s History of Electricity.8vo, 3 

Voltaic Cell.8vo, 3 

Classen’s Quantitative Chemical Analysis by Electrolysis. (Boltwood.). .8vo, 3 

Crehore and Sauier’s Polarizing Photo-chronograph. 8vo. 3 


Dawson’s “Engineering” and Electric Traction Pocket-book.. i6mo, morocco, 5 
Dolezalek’s. Theory of the Lead Accumulator. (Storage Battery.) 
(Shortly.) (Von Ende.) 

Duhem’s Thermodynamics and Chemistry. (Burgess.).8vo, 4 

Flather’s Dynamometers, and the Measurement of Power.nmo, 3 

Gilbert’s De Magnete. (Mottelay.).8vo, 2 

Hanchett’s Alternating Currents Explained.12mo, 1 

Holman’s Precision of Measurements.8vo, 2 

Telescopic Mirror-scale Method, Adjustments, and Tests.Large 8vo, 

Landauer’s Spectrum Analysis. (Tingle.).8vo, 3 

Le Chatelier’s High-temperature Measurements. (Boudouard—Burgess.)nmo, 3 
Lob’s Electrolysis and Electrosynthesis of Organic Compounds (Lorenz.) nmo, 1 

* Lyons’s Treatise on Electromagnetic Phenomena. Vols. I. and II. 8vo, each, 6 

* Michie. Elements of Wave Motion Relating to Sound and Light.8vo, 4 

Niaudet’s Elementary Treatise on Electric Batteries. (Fishoack.).nmo, 2 

* Parshall and Hobart’s Electric Generators.Small 4to. half morocco, 10 

* Rosenberg’s Electrical Engineering. (Haldane Gee—Kinzbrunner.)... .8vo, 1 

Ryan, Norris, and Hoxie’s Electrical Machinery. Vol. 1 .8vo, 2 

Thurston’s Stationary Steam-engines.8vo, 2 

* Tillman’s Elementary Lessons in Heat. 8vo, 1 


9 















































Tory and Pitcher’s Manual of Laboratory Physics 
Ulke’s Modern Electrolytic Copper Refining . . . 


. ... Small 8 vo, 2 00 
.,. 8 vo, 3 00 


LAW. 

* Davis’s Elements of Law.8vo, 2 50 

* Treatise on the Military Law of United States.8vo, 7 op 

* Sheep, 7 50 

Manual for Courts-martial.i6mo, morocco, 1 50 

Wait’s Engineering and Architectural Jurisprudence.8vo, 6 00 

Sheep, 6 50 

Law of Operations Preliminary to Construction in Engineering and Archi¬ 
tecture. 8vo, 5 00 

Sheep, 5 50 

Law of Contracts.. . 8vo, 3 00 

Winthrop’s Abridgment of Military Law.i2mo, 2 50 

MANUFACTURES. 

Bernadou’s Smokeless Powder—Nitro-cellulose and Theory of the Cellulose 

Molecule.nmo, 2 50 

Bolland’s Iron Founder.nmo, 2 50 

“The Iron Founder,” Supplement.nmo, 2 50 

Encyclopedia of Founding and Dictionary of Foundry Terms Used in the 

Practice of Moulding.nmo, 3 00 

Eissler’s Modern High Explosives.8vo, 4 00 

Effront’s Enzymes and their Applications. (Prescott.).8vo, 3 00 

Fitzgerald’s Boston Machinist. i8mo, 1 00 

Ford’s Boiler Making for Boiler Makers.i8mo, 1 00 

Hopkins’s Oil-chemists’ Handbook.8vo, 3 00 

Keep’s Cast Iron.8vo, 2 50 

Leach’s The Inspection and Analysis of Food with Special Reference to State 
Control. (In preparation .) 

Metcalf’s Steel. A Manual for Steel-users.12mo, 2 00 

Metcalfe’s Cost of Manufactures—And the Administration of Workshops, 

Public and Private.,8vo, 5 00 

Meyer’s Modern Locomotive Construction.4to, 1 o 00 

* Reisig’s Guide to Piece-dyeing.8vo, 25 00 

Smith’s Press-working of Metals.*. .8vo, 3 00 

Spalding’s Hydraulic Cement.i2mo, 2 00 

Spencer’s Handbook for Chemists of Beet-sugar Houses.i6mo, morocco, 3 00 

Handbook tor sugar Manufacturers and their Chemists... i6mo, morocco, 2 00 
Thurston’s Manual of Steam-boilers, their Designs, Construction and Opera¬ 
tion.8vo, 5 00 

* Walke’s Lectures on Explosives.8vo, 4 00 

West’s American Foundry Practice.nmo, 2 50 

Moulder’s Text-book.nmo, 2 50 

Wiechmann’s Sugar Analysis.Small 8vo, 2 50 

Wolff’s Windmill as a Prime Mover.8vo, 3 00 

Woodbury’s Fire Protection of Mills.8vo, 2 50 

MATHEMATICS. 

Baker’s Elliptic Functions.8vo, 1 50 

* Bass’s Elements of Differential Calculus.nmo, 4 00 

Briggs’s Elements of Plane Analytic Geometry.nmo, 1 00 

10 


1 





































Compton’s Manual of Logarithmic Computations.i2mo, i 50 

Davis’s Introduction to the Logic of Algebra.8vo, 1 50 

• Dickson’s College Algebra.Large 12mo, 1 50 

• Introduction to the Theory of Algebraic Equations .Large i2mo, 1 25 

Halsted’s Elements of Geometry.8vo, 1 75 

Elementary Synthetic Geometry.8vo. 1 50 

Rational Geometry. (Shortly.) 

♦Johnson’s Three-place Logarithmic Tables: Vest-pocket size.paper, 15 

100 copies for 5 00 

• Mounted on heavy cardboard, 8X10 inches, 25 

10 copies for 2 00 

Elementary Treatise on the Integral Calculus.Small 8vo, 1 50 

Curve Tracing in Cartesian Co-ordinates.i2mo, 1 00 

Treatise on Ordinary and Partial Differential Equations.Small 8vo, 3 50 

Theory of Errors and the Method of Least Squares.nmo, 1 50 

• Theoretical Mechanics.nmo, 3 00 

Laplace’s Philosophical Essay on Probabilities. (Truscott and Emory.) nmo, 2 00 

• Ludlow and Bass. Elements of Trigonometry and Logarithmic and Other 

Tables. 8vo, 3 00 

Trigonometry and Tables published separately...,. Each, 2 00 

Maurer’s Technical Mechanics.8vo, 4 00 

Merriman and Woodward’s Higher Mathematics.8vo, 5 00 

Merriman’s Method of Least Squares. 8vo, 2 00 

Rice and Johnson’s Elementary Treatise on the Differential Calculus.Sm., 8vo, 3 00 

Differential and Integral Calculus. 2 vols. in one.Gmail 8vo, 2 50 

Wood’s Elements of Co-ordinate Geometry.8vo, 2 00 

Trigonometry: Analytical, Plane, and Spherical. . .. nmo, 1 00 

MECHANICAL ENGINEERING. 

MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS. 

Baldwin’s Steam Heating for Buildings.nmo, 2 50 

Barr’s Kinematics of Machinery.8vo, 2 50 

• Bartlett’s Mechanical Drawing.8vo, 3 00 

• “ “ “ Abridged Ed.8vo, 1 50 

Benjamin’s Wrinkles and Recipes.nmo, 2 00 

Carpenter’s Experimental Engineering.8vo, 6 00 

Heating and Ventilating Buildings. 8 vo, 4 00 

Cary’s Smoke Suppression in Plants using Bituminous Coal. (In prep¬ 
aration.) 

Clerk’s Gas and Oil Engine.Small 8vo, 4 00 

Coolidge’s Manual of Drawing.8vo, paper, 1 00 

Cromwell’s Treatise on Toothed Gearing.nmo, 1 50 

Treatise on Belts and Pulieys.nmo, 1 50 

Durley’s Kinematics bf Machines.8vo, 4 00 

Flather’s Dynamometers and the Measurement of Power.nmo, 3 00 

Rope Driving.nmo, 2 00 

Gill’s Gas and Fuel Analysis for Engineers.nmo, 1 25 

Hall’s Car Lubrication. ■ •. .nmo, 1 00 

Hutton’s The Gas Engine.8vo, 5 00 

Jones’s Machine Design: 

Part I.—Kinematics of Machinery.8vo, 1 50 

Part II.—Form, Strength, and Proportions of Parts.8vo, 3 00 

Kent’s Mechanical Engineer’s Pocket-book.i6mo, morocco, 5 00 

Kerr’s Power and Power Transmission.8vo, 2 00 

MacCord’s Kinematics; or, Practical Mechanism. 8 vo, 5 00 

Mechanical Drawing.4to, 4 00 

Velocity Diagrams. 8 vo, 1 50 


11 














































Mahan’s Industrial Drawing. (Thompson.).8vo, 3 5® 

Poole’s Calorific Power of Fuels.8vo, 3 oo 

Reid’s Course in Mechanical Drawing.8vo. 2 oo 

Text-book of Mechanical Drawing and Elementary Machine Design. .8vo, 3 00 

Richards’s Compressed Air.i2mo, 1 50 

Robinson’s Principles of Mechanism. 8vo, 3 00 

Smith’s Press-working of Metals. 8vo f 3 00 

Thurston’s Treatise on Friction and Lost Work in Machinery and Mill 

Work.8vo, 3 00 

Animal as a Machine and Prime Motor, and the Laws of Energetics. 12mo, 1 00 

Warren's Elements of Machine Construction and Drawing.8vo, 7 50 

Weisbach’s Kinematics and the Power of Transmission. Herrmann— 

Klein.).8vo, 5 00 

Machinery of Transmission and Governors. (Herrmann—Klein.). .8vo, 500 

Hydraulics and Hydraulic Motors. (Du Bois.).8vo, 5 00 

Wolff’s Windmill as a Prime Mover.8vo, 3 00 

Wood’s Turbines.8vo, 2 50 

* 

MATERIALS OF ENGINEERING. 

Bovey’s Strength of Materials and Theory of Structures.8vo, 7 50 

Burr’s Elasticity and Resistance of the Materials of Engineering. 6th Edition, 

Reset....8vo. 7 50 

Church’s Mechanics of Engineering.8vo, 6 00 

Johnson’® Materials of Construction..Large 8vo, 6 00 

Keep’s Cast Iron.8vo, 2 50 

Lanza’s Applied Mechanics.8vo, 7 50 

Martens’s Handbook on Testing Materials. (Henning.).8vo, 7 50 

Merriman’s Text-book on the Mechanics of Materials.8vo, 4 00 

Strength of Matermls.nmo, 1 00 

Metcalf’s Steel. A Manual for Steel-users.i2mo 2 00 

Smith's Materials of Machines.i2mo 1 00 

Thurston’s Materials of Engineering.3 vols , Svo, 8 00 

Part II.—Iron and Steel.8vo, 3 50 

Part IH.—A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents.8vo 2 50 

Text-book of the Materials of Construction.8vo, 5 00 

Wood’s Treatise on the Resistance of Materials and an Appendix on the 

Preservation of Timber.Svo, 2 00 

Elements of Analytical Mechanics.8vo, 3 00 

Wood’s Rustless Coatings. {Shortly.) 

STEAM-ENGINES AND BOILERS. 

Carnot’s Reflections on the Motive Power of Heat. (Thurston.).nmo, 1 50 

Dawson's “Engineering” and Electric Traction Pocket-book. .i6mo, mor., 5 00 

Ford’s Boiler Making for Boiler Makers.i8mo, 1 00 

Goss’s Locomotive Sparks. . 8vo, 2 00 

Hemenway’s Indicator Practice and Steam-engine Economy.nmo. 3 00 

Hutton’s Mechanical Engineering of Power Plants.8vo. 5 00 

Heat and Heat-engines.8vo, 5 00 

Kent’s Steam-bo’ler Economy.8vo, 4 00 

Kneass’s Practice and Theory of the Injector.8vo 1 50 

MacCord’s Slide-valves.8vo, 2 00 

Meyer’s Modern Locomotive Construction.4to, 10 00 

12 










































Peabody’s Manual of the Steam-engine Indicator.i2mo, i 50 

Tables of the Properties of Saturated Steam and Other Vapors.8vo, 1 00 

Thermodynamics of the Steam-engine and Other Heat-engines. . . . 8vo, 5 00 

Valve-gears for Steam-engines.8vo, 2 50 

Peabody and Miller’s Steam-boilers.8vo, 4 00 

Pray’s Twenty Years with the Indicator.Large 8vo, 2 50 

Pupln’s Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. 

(Osterberg.).i2mo, 1 25 

Reagan’s Locomotives : Simple, Compound, and Electric.121110, 2 50 

Rontgen’s Principles of Thermodynamics. (Du Bois.).8vo, 5 00 

Sinclair’s Locomotive Engine Running and Management.nmo, 2 00 

Smart’s Handbook of Engineering Laboratory Practice.i2mo, 2 50 

Snow’s Steam-boiler Practice.8vo, 3 00 

Spangler’s Valve-gears.8vo, 2 50 

Notes on Thermodynamics.....121110, 1 00 

Spangler, Greene, and Marshall’s Elements of Steam-engineering.8vo, 3 00 

Thurston’s Handy Tables.8vo. 1 50 

Manual of the Steam-engine .2 vols.. 8vo, 10 00 

Part I.—History, Structuce, and Theory.8vo, 6 00 

Part II.—Design, Construction, and Operation.8vo, 6 00 

Handbook of Engine and Boiler Trials, and the Use of the Indicator and 

the Prony Brake.8vo 5 o* 

Stationary Steam-engines.8vo, 2 50 

Steam-boiler Explosions in Theory and in Practice.nmo 1 50 

Manual of Steam-boilers, Their Designs, Construction, and Operation. 8vo, 5 00 

Weisbach’s Heat, Steam, and Steam-engines. (Du Bois.).8vo,; 5 00 

Whitham’s Steam-engine Design. 8vo, 5 00 

Wilson’s Treatise on Steam-boilers. (Flather.). ... .i6mo, 2 50 

Wood’s Thermodynamics Heat Motors, and Refrigerating Machines... .8vo, 4 00 

MECHANICS AND MACHINERY. 

Barr’s Kinematics ot Machinery.8vo, 2 50 

Bovey’s Strength of Materials and Theory of Structures. 8 vo, 7 50 

Chase’s The Art of Pattern-making.nmo, 2 50 

Chordal.—Extracts from Letters.nmo, 2 00 

Church’s Mechanics of Engineering.8vo, 6 00 

Notes and Examples in Mechanics.8vo, 2 00 

Compton’s First Lessons in Metal-working.nmo, 1 50 

Compton and De Groodt’s The Speed Lathe.nmo, 1 50 

Cromwell’s Treatise on Toothed Gearing.nmo, 1 50 

Treatise on Belts and Pulleys .i2mo, 1 50 

Dana’s Text-book of Elementary Mechanics for the Use of Colleges and 

Schools.nmo, 1 50 

Dingey’s Machinery Pattern Making.nmo, 2 00 

Dredge’s Record of the Transportation Exhibits Building of the World’s 

Columbian Exposition of i 8 q 3 .4to, half morocco, 5 00 

Du Bois’s Elementary Principles of Mechanics: 

Vol. I.—Kinematics.8vo, 3 50 

Vol H.—Statics.8vo, 4 00 

Vol. III.—Kinetics.8vo, 350 

Mechanics of Engineering. Vol. I.Small 4to, 7 50 

Vol. II.Small 4to, 10 00 

Durley’s Kinematics of Machines.8vo, 4 00 

Fitzgerald’s Boston Machinist.i6mo, 1 00 

Flather’s Dynamometers, and the Measurement of Power.nmo, 3 00 

Rope Driving .i2mo, 2 00 

Goss’s Locomotive Sparks. .....8vo, 2 00 


13 



















































Hall’s Car Lubrication. . i2mo, i oo 

Holly’s Art of Saw Filing. .,.i8mo 75 

* Johnson’s Theoretical Mechanics.nmo, 3 00 

Statics by Graphic and Algebraic Methods.8vo. 2 00 

Jones’s Machine Design: 

Part I.—Kinematics of Machinery.8vo, 1 50 

Part II.—Form, Strength, and Proportions of Parts.8vo, 3 00 

Kerr’s Power and Power Transmission.8vo, 2 00 

Lanza’s Applied Mechanics. 8vo, 7 50 

MacCord’s Kinematics; or, Practical Mechanism.8'0, 5 00 

Velocity Diagrams . 8vo, 1 5° 

Maurer’s Technical Mechanics.8vo, 4 00 

Merriman’s Text-book on the Mechanics of Materials. 8vo, 4 00 

* Michie’s Elements of Analytical Mechanics.8vo, 4 00 

Reagan’s Locomotives: Simple, Compound, and Electric.i2mo, 2 50 

Reid’s Course in Mechanical Drawing.8vo, 2 00 

Text-book of Mechanical Drawing and Elementary Machine Design. .8vo, 3 00 

Richards’s Compressed Air.i2mo, 1 50 

Robinson’s Principles of Mechanism.8vo, 3 00 

Ryan, Norris, and Hoxie’s Electrical Machinery. Vol. 1 .8vo, 2 50 

Sinclair’s Locomotive-engine Running and Management.12mo, 2 00 

Smith’s Press-working of Metals .8vo, 3 00 

Materials of Machines. ... . . .i2mo, 1 00 

Spangler, Greene, and Marshall’s Elements of Steam-engineering.8vo, 3 00 

Thurston’s Treatise on Friction and Lost Work in Machinery and Mill 

Work. .. .. 8vo, 3 00 

Animal as a Machine and Prime Motor, and the Laws of Energetics, nmo, 1 00 

Warren’s Elements of Machine Construction and Drawing.8vo, 7 50 

Weisbach’s Kinematics and the Power of Transmission. (Herrmann— 

Klein.). 8vo, 5 00 

Machinery of Transmission and Governors. (Herrmann—Klein.).8vo, 5 00 

Wood’s Elements of Analytical Mechanics.8vo, 3 00 

Principles of Elementary Mechanics.nmo, x 25 

Turbines.8vo, 2 50 

The World’s Columbian Exposition of 1893.4to, 1 00 

METALLURGY. 

Egleston’s Metallurgy of Silver, Gold, and Mercury: 

Vol. I.—Silver.8vo, 7 50 

Vol. II.—Gold and Mercury.8vo, 7 50 

** Iles’s Lead-smelting. (Postage 9 cents additional.).12m©, 2 50 

Keep’s Cast Iron.8vo, 2 50 

Kunhardt’s Practice of Ore Dressing in Europe.8vo, 1 50 

Le Chatelier’s High-temperature Measurements. (Boudouard—Burgess.). i2mo, 3 00 

Metcalf’s Steel. A Manual for Steel-users.nmo, 2 00 

Smith’s Materials of Machines.i2mo, 1 00 

Thurston’s Materials of Engineering. In Three Parts.8vo, 8 00 

Part II.—Iron and Steel.8vo, 3 50 

Part III.—A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents.8vo, 2 50 

Ulke’s Modern Electrolytic Copper Refining.8vo, 3 00 

MINERALOGY. 

Barringer’s Description of Minerals of Commercial Value. Oblong, morocco, 2 50 

Boyd’s Resources of Southwest Virginia..8vo. 3 00 

Map of Southwest Virginia.Pocket-book form, 2 00 


14 















































Brush’s Manual of Determinative Mineralogy. (Penfield.).8vo, 4 00 

Chester s Catalogue of l^Iinerals...8vo t paper, 1 00 

Cloth, 1 25 

Dictionary of the Names of Minerals. 8vo, 3 50 

Dana’s System of Mineralogy.,.Large 8vo, half leather, 12 50 

First Appendix to Dana’s New “System of Mineralogy.’’_Large 8vo, 1 00 

Text-book of Mineralogy.8vo, 4 00 

Minerals and How to Study Them.i2mo, 1 50 

Catalogue of American Localities of Minerals.Large 8vo, 1 00 

Manual of Mineralogy and Petrography .i2mo, 2 00 

Eakle’s Mineral Tables.8vo, 1 25 

Egleston’s Catalogue of Minerals and Synonyms. 8vo, 2 50 

Hussak’s The Determination of Rock-forming Minerals. (Smith.) Small 8vo, 2 00 

Merrill’s Non-Metallic Minerals. (Shortly.) 

* Penfield’s Notes on Determinative Mineralogy and Record of Mineral Tests. 

8vo, paper, o 50 

Rosenbusch’s Microscopical Physiography of the Rock-making Minerals. 

(Iddings.).8vo, 5 00 

* Tillman’s Text-book of Important Minerals and Docks. 8vo, 2 00 

Williams’s Manual of Lithology.8vo, 3 00 

MINING. 

Beard’s Ventilation of Mines.i2mo, 2 50 

Boyd’s Resources of Southwest Virginia.8vo, 3 00 

Map of Southwest Virginia.Pocket-book form, 2 00 

* Drinker’s Tunneling, Explosive Compounds, and Rock Drills. 

4to, half morocco, 25 00 

Eissler’s Modern High Explosives.8vo, 4 00 

Fowler’s Sewage Works Analyses.i2mo, 2 00 

Goodyear’s Coal-mines of the Western Coast of the United States.i2mo, 2 50 

Ihlseng’s Manual of Mining.8vo, 4 00 

** Iles’s Lead-smelting. (Postage qc. additionaL).nmo, 2 50 

Kunhardt's Practice of Ore Dressing in Europe.8vo, 1 50 

O’Driscoll’s Notes on the Treatment of Gold Ores.8vo, 2 00 

* Walke’s Lectures on Explosives.8vo, 4 00 

Wilson’s Cyanide Processes.i2mo, 1 50 

Chlorination Process.nmo, 1 50 

Hydraulic and Placer Mining.12mo, 2 00 

Treatise on Practical and Theoretical Mine Ventilation.nmo 1 25 

SANITARY SCIENCE. 

Copeland’s Manual of Bacteriology. (In preparation.) 

Folwell’s Sewerage. (Designing, Construction and Maintenance.).8vo, 3 00 

Water-supply Engineering.....8vo, 4 00 

Fuertes’s Water and Public Health.nmo, 1 50 

Water-filtration Works.nmo, 2 50 

Gerhard’s Guide to Sanitary House-inspection.i6mo, 1 00 

Goodrich’s Economical Disposal of Town’s Refuse.Demy 8vo, 3 50 

Hazen’s Filtration of Public Water-supplies.8vo, 3 00 

Kiersted’s Sewage Disposal. nmo, 1 25 

Leach’s The Inspection and Analysis of Food with Special Reference to State 
Control. (In preparation.) 

Mason’s Water-supply. (Considered Principally from a Sanitary Stand¬ 
point.) 3d Edition, Rewritten.8vo, 4 00 

Examination of Water. (Chemical and Bacteriological.).nmo, 1 25 

15 








































Merriman’s Elements of Sanitary Engineering .8vo, 

Nichols’s Water-supply. (Considered Mainly from a Chemical and Sanitary 

Standpoint.) (1883.).8vo, 

Ogden’s Sewer Design.i2mo, 

•Price’s Handbook on Sanitation.i2mo, 

Richards’s Cost of Food. A Study in Dietaries.i2mo. 

Cost of Living as Modified by Sanitary Science.i2mo, 

Richards and Woodman’s Air, Water, and Food from a Sanitary Stand¬ 
point.8vo, 

• Richards and Williams’s The Dietary Computer.8vo, 

Rideal’s Sewage and Bacterial Purification of Sewage.8vo, 

Turneaure and Russell’s Public Water-supplies.8vo, 

Whipple’s Microscopy of Drinking-water.8vo, 

Woodhull’s Notes and Military Hygiene.i6mo, 


MISCELLANEO OS. 

Barker’s Deep-sea Soundings.8vo, 

Emmons’s Geological Guide-book of the Rocky Mountain Excursion of the 

International Congress of Geologists.Large 8vo, 

Ferrel’s Popular Treatise on the Winds.8vo, 

Haines’s American Railway Management.i2mo, 

Mott’s Composition.'Digestibility.and Nutritive Value of Food. Mounted chart. 

Fallacy of the Present Theory of Sound.i6mo, 

Ricketts’s History of Rensselaer Polytechnic Institute, 1824-1804. Small 8vo, 

Rotherham’s EmpHasized New Testament.Large 8vo. 

Steel’s Treatise on the Diseases of the Dog.8vo, 

Totten’s Important Question in Metrology.8vo, 

The World’s Columbian Exposition ot 1893.4to, 

Worcester and Atkinson. Small Hospitals, Establishment and Maintenance, 
and Suggestions for Hospital Architecture, with Plans for a Small 
Hospital.i2mo, 

HEBREW AND CHALDEE TEXT-BOOKS. 

Green’s Grammar of the Hebrew Language.8vo, 

Elementary Hebrew Grammar.i2mo, 

Hebrew Chrestomathy.8vo, 

Gesenius’s Hebrew and Chaldee Lexicon to the Old Testament Scriptures. 

(Tregelles.).Small 4to, half morocco, 

Letteris’s Hebrew Bible.8vo, 


2 00 

2 50 
2 00 
1 50 
1 00 

1 00 

2 00 
1 50 

3 50 
5 00 
3 50 
I 50 


2 00 

1 50 
4 00 

2 50 
1 25 

1 00 

3 00 

2 00 

3 50 
2 50 
1 00 


I 25 


3 00 

1 25 

2 OO 

5 00 
2 25 


16 























































. 





* 















































































■ 
































































MAR 36 1904 








































































